The development of an instrument for measuring teachers’ and students’ beliefs about differentiated instruction and teaching in heterogeneous chemistry classrooms

1.1 Theoretical framework: DI in a heterogeneous chemistry classroom

Class heterogeneity has many dimensions: students’ learning ability, prior knowledge, family background, socioeconomic background, gender and learning preferences, race, learning difficulties, language problems, and more (Ortiz-Rodríguez et al., 2021). In education research, the term heterogeneity is used to describe the mixed ability classrooms as well as combining regular learners with special ability and disability learners in the same class (Blonder et al., 2014; Kizilaslan et al., 2020).

Today’s classes are becoming increasingly heterogeneous (Santangelo & Tomlinson, 2012). Meeting the needs of all learners in these heterogeneous classes is one of the urgent concerns in education (Konstantinou-Katzi et al., 2013). However, currently teachers do not have enough knowledge or training in how to teach in heterogeneous classrooms (Mumba et al., 2015). This is also the situation in chemistry teaching (Easa & Blonder, 2022). Teachers often do not know their students well enough to even identify their needs (Woollacott et al., 2014). As a result, all teachers at different education levels find themselves unprepared to adjust their teaching to all learners with different needs (Kousa et al., 2018).

On the other hand, some studies indicate that it is almost impossible for teachers to consider all the needs of all their students, due to students’ different backgrounds (Lambe & Bones, 2006), and due to the time and effort required to implement differentiated teaching as an effective teaching method (Valiandes, 2015). However, when DI is applied, it pays off, and leads to great benefits to the whole class (Janney & Snell, 2006), of students’ motivation, commitment, subject understanding, learning and achievements (Konstantinou-Katzi et al., 2013; Lambe & Bones, 2006; Valiandes, 2015), of self-esteem, confidence, and gap achievement between the students (Norman et al., 1998).

According to the literature, several factors influence teachers’ attitudes towards heterogeneity in the classroom; these include teachers’ professional training, teachers’ age, gender, and students’ abilities (Alnahdi, et al., 2019; Avramidis & Norwich, 2002; De Boer et al., 2011; Orakci et al., 2016). A positive correlation between teachers’ attitudes towards heterogeneity and the implementation of customized teaching practices in the classroom, a belief in the importance and acceptance of heterogeneity as well as the integration of different learners in the classroom were reported. However, difficulties in implementing customized teaching practices are due to lack of training and proper tools to deal with it. In addition, there was a negative correlation between age and seniority in teaching with implementing customized teaching in the classroom. Moreover, there was a significant connection between gender and a positive attitudes towards heterogeneity as well as the implementation of personalized teaching to benefit women. However, studies that empirically investigated the impact of personalized teaching in heterogeneous classrooms are scarce. In two recent reviews, Guillemot et al. (2022) and Van Steen et al. (2020) reported that implementing inclusive teaching did not result in clear findings regarding teachers’ attitudes before and after the implementation. This can result from teachers’ difficulties in implementing differentiated teaching practices despite their belief in its importance and their positive attitudes towards it (Van Casteren et al., 2017). In addition, the lack of support and insufficient professional training for teachers, on the part of the school management as well as the policy to implement personalized teaching in heterogeneous classes inhibited its use in heterogeneous classes (Tomlinson, 2014a).

Here, we refer to the class as a single heterogeneous unit, expressing all the heterogeneous forms discussed above; however, we will consider one important form of heterogeneity in the chemistry classroom in high school, namely, the different misconceptions that learners hold of chemistry learned (Tomlinson, et al., 2003). The DI term is used by applying a variety of differentiated teaching strategies aimed to address different misconceptions (Winstanley, 2016). To ensure that the DI will meet the diverse needs and profiles of different students, considering their different misconceptions in chemistry, customized pedagogical kits (CPKs) were designed to enable teachers to apply DI in chemistry teaching (Easa & Blonder, 2022). The CPKs comprise varied pedagogical activities that were designed as treatments, to help chemistry teachers personalize their teaching according to students’ misconceptions. Each kit includes a diagnostic task, its characterization, pedagogical treatments for diagnosed misconceptions, and an assessment task, to evaluate the effectiveness of the treatments implemented in the classroom. Next, we will review the literature related to the research variables and their connection to DI.

1.2 Teachers’ self-efficacy beliefs and attitudes towards DI

Studies have shown that teachers are the key factor in the success of any educational innovation attempt (e.g., Hattie, 2009). Effective educational practices (e.g., DI practices) would occur when the attitudes of teachers and their self-efficacy beliefs are generally taken seriously (Chen & Wei, 2015). Therefore, investigating the teachers’ attitudes and personal beliefs is a necessary first step if any attempt to change the teaching methods is to be achieved (Van Driel et al., 2007). Hence, in the current study, we chose to investigate those variables.

Attitudes : In education research, there is an agreement that an attitude is the tendency to think, feel, or act positively or negatively toward objects in the environment (Haddock & Maio, 2014). Since attitudes have been defined in literature as strongly related to actions, they play a crucial role in teachers’ instruction in the classroom (Baumert & Kunter, 2013). Attitudes consist of three components: emotional, cognitive, and behavioral components.

Many researchers claim that teachers’ attitudes influence their teaching abilities in heterogeneous classes (e.g., Baumert & Kunter, 2013), and is influenced by the quality of professional training they received (Hartwig & Schwabe, 2018). Other researchers even claim that attitudes are a mediating factor between teacher training and the implementation of DI in the classroom (Hartwig & Schwabe, 2018). Moreover, other findings have shown a strong correlation between teachers’ positive attitudes and the implementation of inclusion practices in their heterogeneous classrooms (Schwab et al., 2018).

Self-efficacy is defined as people’s beliefs about their ability to produce designated levels of performance that influence events that affect their lives. Self-efficacy beliefs determine how people feel, think, motivate themselves, and behave. Such beliefs produce these diverse effects through four major processes (Bandura, 1997). They include cognitive, motivational, affective, and selection processes (Bandura, 1994). These beliefs affect a person’s behavior, choices, efforts, ability to cope and persevere in various tasks of life (Bandura, 1997). Teachers with high self-efficacy beliefs have more confidence in their ability to teach in diverse classes, and manage functioning classroom (Blonder, Benny & Jones, 2014). Moreover, teachers’ positive self-efficacy beliefs are related to the success of students in the classroom (Jarvis & Pell, 2005), and teachers’ negative self-efficacy beliefs increases with the level of students’ difficulties and differences (Avramidis et al., 2000). Additionally, (Rachmatullah et al., 2022) who have classified the participating teachers into four categories according to the literature, found that teachers with more positive attitudes towards science were more likely to fall into the category of teachers with higher self-efficacy. However, teachers who are used to teaching diverse classes or apply DI regularly have more positive beliefs towards teaching, and they are more positive about their ability to teach diverse students (Avramidis et al., 2000; Konstantinou-Katzi et al., 2013). On other hand, teachers do not have enough knowledge or skills on how to deal with diversity (Benny & Blonder, 2018). They lack suitable resources, teaching materials, and methods (Norman et al., 1998), teaching time, properly planned training, or suitable professional development courses (Avramidis et al., 2000; Lambe & Bones, 2006).

1.3 Students’ self-efficacy beliefs, pedagogical involvement, and attitudes towards chemistry and DI

According to some empirical evidence, students’ attitudes and self-efficacy (beliefs about their ability and skills) were found to be dominant predictors of their achievement, not excluding science achievement (Roebianto, 2020). Therefore, we will also examine students’ self-efficacy and attitudes toward differentiated teaching.

Self-efficacy: Attributions are factors that are perceived as reasons for results. Attribution theory assumes that people strive to explain the causes of significant events (Heider, 1958; Weiner, 1979). In achievement situations, students often attribute their successes or failures to factors such as ability, effort, task difficulty, or luck (Weiner, 1979). Attributions affect expectations for future successes. Students can attribute past successes primarily to stable factors, which the student cannot control, such as high ability or easy tasks, and unstable factors, such as high effort, which students can control. Students who attribute their success to stable factors tend to have higher expectations for success than those who attribute their success to unstable factors (Weiner, 1979). According to Bandura (1986) and to the theory of self-efficacy, attributions are one type of clue that students use to assess their self-efficacy. Moreover, attribution factors, such as effort invested and judgments of the task difficulty, indirectly affect performance through self-efficacy. For example, students who succeed through much effort tend to judge themselves as less capable than those who succeed easily. Success in a task that is judged as easy will not increase self-efficacy as much as success in a difficult task. Self-efficacy depends on attributive factors, as well as other influences, such as situational circumstances in which performance occurs, the number of successes, the pattern of the success, and the credibility of the persuader (Britner & Pajares, 2006; Weiner, 1979).

Attitudes: When students hold negative attitudes towards science and scientists, it adversely affects their attitudes towards the choice of scientific trends, and the future choice of science-related professions (e.g., Broman et al., 2011). Attitudes towards science are influenced by preference for disciplines, curricula, teachers’ beliefs, and teaching methods (Khan & Ali, 2012). Moreover, according to Ozel et al. (2013), attitudes have an impact on academic achievement, and positive attitudes toward chemistry have been shown to lead to better achievements in chemistry. Educational interventions that impact students’ attitudes are important to consider because attitudes tend to decline over time (Potvin & Hasni, 2014). Hence the importance of the intervention in the current study, which refers to the implementation of the CPKs in the chemistry classroom, and the examination of its effect on the attitudes and self-efficacy of the students and teachers, and as a result on their achievements.

1.4 Involvement of students in classroom DI pedagogy

In recent years student involvement in educational decision-making and classroom pedagogy has been actively embraced in school planning (Rudduck & Fielding, 2006). The most relevant way of embracing student pedagogical involvement, according to (Sugai & Horner, 2009), is when students who aware of the rationale of their education and pedagogy ways believe that they can choose their education options, so they make a psychological investment in learning, they strive to learn what the teacher offers, and they feel pride not only in receiving the formal indicators of success (scores), but in understanding the material and internalizing it into their lives. As a result, all kinds of students, became more involved in their learning, more interacted with the pedagogical activities, more likely to be interested in understanding the material and concepts being taught, and wanting to succeed.

We therefore suggest that involving students in the DI pedagogy might impact their attitudes towards DI, chemistry, and self-efficacy. This is in line with several studies that indicate that interaction in learning is considered as the core of the learning experience and a necessary condition for successful learning (Picciano, 2006). A high level of interaction between teachers and students and between the students themselves may have a positive effect on involvement in learning and on student’s motivation, achievements afterwards (Lee & Hung, 2012). Interactions relate to three dimensions: interactions with content, with the teacher, and with other learners. Interactions with the content indicate the student’s interest in the material being taught, interactions with the teacher indicate the teacher’s ability to influence the student’s meaning of the material being studied, and interactions with other learners indicate the extent to which discussions and collaborations take place between learners.

1.5 Research goals and questions

There are a limited number of tools that investigate differentiate teaching in heterogeneous classes, evaluate and measure teachers’ and students’ beliefs toward DI (e.g., Van de Grift, 2014). However, there is no instrument for measuring this construct in chemistry teaching and learning (Sirhan, 2007). Hence, there is a need to develop tools to examine the beliefs of students and teachers towards DI in heterogeneous classes. Here we describe the development and validation of questionnaires regarding DI. The questionnaires were tested in a controlled experiment, which will be further described.

The goal of the research was to examine and better understand the influence of CPKs which were activated in heterogeneous classes, on teachers’ self-efficacy and attitudes towards teaching in heterogeneous classes and towards DI pedagogy as well as the students’ self-efficacy and attitudes towards the importance of chemistry and DI pedagogy in high school within the CPKs, through three research questions:

1. How, and to which extent, did the CPKs affect high school chemistry teachers in:

   1. Self-efficacy beliefs, and

   2. Attitudes towards DI?

2. How did the CPKs affect high-school chemistry teachers’ attitudes and self-efficacy beliefs regarding teaching heterogeneous classes?

3. How, and to which extent, did students’ involvement in the pedagogy of DI approach affect high school chemistry students in:

   1. Self-efficacy beliefs,

   2. Attitudes towards differentiated instruction, and

   3. Attitudes towards the importance of chemistry?

We expect the CPK interventions will have a positive effect on students’ (Dalgety et al., 2003) and teachers’ (Schwab et al., 2018) attitudes and self-efficacy and on teachers’ and attitudes regarding teaching at heterogeneous classes. We expect that students who were pedagogically involved in the DI pedagogy will report higher positive attitudes and self-efficacy beliefs than those who were not involved (Abdous, 2019; Lee & Hung, 2012).

1.6 Methodology

1.7 The development and validation of the research questionnaires

Examining self-efficacy’s place in DI and teachers’ attitudes towards DI within heterogeneous classrooms requires a tool that can be easily managed and that can combine relevant concepts used in the research literature (e.g., attitudes towards science teaching, chemistry teaching, teaching methods, innovative teaching, differentiated instruction (DI), and customized teaching-based practices).

1. Teachers’ questionnaire of their attitudes and self-efficacy when teaching heterogeneous classes and DI: the development and validation stages

We conducted the following steps for the development and validation of 1. Teachers’ questionnaire of attitudes and self-efficacy for teaching at heterogeneous classes and DI.

1. Creating a pool of 76 items for the questionnaire was based on three sources:

   1. Published questionnaires from relevant literature, related to general and scientific attitudes, teaching methods (Gibson and Dembo, 1984), general and scientific self-efficacy (Foy et al., 2013), and classroom practices to achieve understanding (Kerlinger, 1967).

   2. Relevant literature regarding DI, as it was presented in the introduction (e.g., Tomlinson, 2014b).

   3. Statements and reactions of teachers who participated in professional development about teaching chemistry in a heterogeneous class and the DI approach. The teachers who implemented the CPKs discussed their students’ reactions and reflected upon their own experiences of teaching chemistry in a heterogeneous chemistry classroom in general and with the CPKs.

2. Grouping of the items from different sources:

   Several examples of this process are described next:

3. A literature-based item was taken from Foy et al. (2013) “How confident do you feel to adapt your teaching to engage students’ interest?” It was adjusted to: “I can motivate students who show little interest in school studies.”

4. Another literature-based item was taken from Foy et al. (2013) “How confident do you feel to provide challenging tasks for capable students?” It was adjusted to: “I can provide a challenge for high-achieving students.”

5. The teachers’ experience-based example is: “When a student is having difficulty with an assignment, I am usually able to adjust it to his/her level”. It was adjusted to: “I can provide my students with chosen options of tasks within the type and format they are supposed to use”.

Later, the items were translated to Hebrew and Arabic.

1. Validation by a panel of experts:

   The items we developed were examined by seven science and education experts, who are also chemistry teachers. Based on their suggestions, we corrected the wording of some of the items (Fortus & Vedder-Weiss, 2014; Schwarzer & Hallum, 2008).

   1. For example: The item: “How much can you prevent a small number of problematic students from ruining an entire lesson?” was rephrased to: “To what extent can you control disruptive behaviors in your classroom?”

2. Validation by a field test:

   87 in-service chemistry teachers, who participated in professional development, for a pilot run, filled-in the questionnaire and were asked to emphasize the reflection and comments they reported regarding the items and their clarity. Accordingly, the wording of some items changed.

   1. For example: The item: “I can motivate students who show little interest in studies” was rephrased to: “To what extent can you motivate students who show little interest in studies?”

3. Item Analysis:

   To select the valid items for the final questionnaire, the item “total correlation coefficient” was calculated. Items that were significant at the 0.000 level and had an r value equal to or higher than 0.403 were selected for the final scale. Following the criteria stated above, 55 items out of 76 were selected.

4. Validation of the structure and content by factor analysis:

   A confirmatory factor analysis (CFA) was performed to extract five factors, as reported in similar studies (e.g., Alsalhi et al., 2021). The analysis confirmed two factors about teachers’ attitudes:

   1. Teachers Attitudes and Beliefs regarding Differentiated Instruction-TABDI.

   2. Teachers Attitudes and Beliefs regarding Practicing Differentiated Instruction-TABPDI.

5. As a result, 12 low-loaded items were deleted. And three factors of teachers’ self-efficacy:

   1. Teachers’ Self-efficacy Beliefs for Practices Differentiated Instruction-TSEBPDI

   2. Teachers’ Self-efficacy Beliefs for Differentiated Instruction-TSEBDI

   3. Self-efficacy to reach all students-TSERCH

6. As a result, 9 low-loaded items were deleted (see Table1).

7. Performing reliability analysis by the Split half method:

   Basically, internal reliability determines whether the questionnaire is homogeneous, i.e., whether all items test the same content area. Therefore, at this stage the Cronbach’s alpha values were tested for the five factors within their items.

8. Revising Cronbach’s alpha values by items, changing or deleting low-loaded items according to our subjective perception:

   Cronbach’s alpha values were re-examined after deleting low-loaded items whose deletion improved the Cronbach’s alpha value of their factors (see Appendix C, where the final items and the reliability values are associated with the relevant factors, and according to the numbering in the original questionnaire).

1. Student questionnaire for attitudes and self-efficacy

The students’ questionnaire was based on two main sources for items:

1. Former questionnaires from relevant literature, related to general and scientific attitudes, general and scientific self-efficacy, teaching methods, integration of technology in teaching chemistry, and classroom practices to achieve understanding (Foy et al., 2013; Gibson and Dembo, 1984; Kerlinger, 1967).

2. Statements and reactions of teachers who participated in professional development about teaching chemistry in a heterogeneous classroom and the DI approach. The teachers who implemented the CPKs discussed their students’ reactions and reflected upon their own experiences of teaching chemistry in a heterogeneous chemistry classroom in general and with the CPKs.

Similarly, to the development process described above, the students’ questionnaire included several stages of development.

Students’ questionnaire regarding attitudes and self-efficacy for DI: the development and validation stages

1. Grouping of the items from different sources:

Based on the sources of the items we described earlier, we grouped the items we formulated in light of the operative and nominal definitions of our research variables (students’ attitudes and self-efficacy) regarding literature, the items offered or drafted by the teachers that participated in the professional development frameworks at the Institute of the authors when they taught chemistry in a heterogeneous classroom and finally, the drafted items from the ready-made questionnaires that already exist in the relevant literature. After selecting and formulating 45 items related to self-efficacy and the attitudes of the high school chemistry students, we translated them to Hebrew and Arabic. The alignment of the items to the study objectives and variables were examined. Several examples of this process are described next:

A literature-based item was taken from Foy et al., (2013) “I enjoy learning science”

It was adjusted to “Science is enjoyable”.

1. Reading test (readability):

The readability of the items was verified by a cognitive pre-testing procedure (Karabenick et al. (Fortus & Vedder-weiss, 2014)) involving 24, eleventh grade students. The students were asked to read each item and select the appropriate degree of their understanding of the items. Documentation and observations of the students’ responses and reflections were preserved. The items were corrected accordingly:

1. The literature-based item “It is important to let the student choose which way he wants to learn”.

It was adjusted to “It is important and necessary to let the student choose which way he wants to learn”.

1. Field test:

The items were handed over to 130 chemistry students of teachers who had participated in a community of chemistry leading teachers at Institute of the authors for a pilot run. A total of 114 completed questionnaires were returned. There were no significant changes in the items, accordingly.

1. Item Analysis:

To select the valid items for the final study, an item “total correlation coefficient” was calculated. Items that were significant at the 0.000 level and the r value was equal to or greater than 0.403 were selected for the final scale. Following the criteria stated above, 38 items out of 45 were selected.

1. Validation of content and structure by performing factor analysis:

Confirmatory factor analysis (CFA) was performed to extract three factors, as reported in similar former studies to examine students’ beliefs (e.g., Maio et al., 2010).

The analysis confirmed three factors regarding attitudes:

1. Students Attitudes towards the Importance of Chemistry-SAIC

2. Students Attitudes towards Practicing DI-SAPDI

3. Attitudes towards Non-Frontal Teaching Methods in Chemistry: ANFTMC. Accordingly, 7 low-loaded items were deleted.

In addition to the confirmation of two factors of self-efficacy, as reported in similar studies (e.g., Schunk, 1989b), the analysis confirmed the existence of two self-efficacy factors:

1. Students Self-Efficacy in Performance Chemistry-SSEPC

2. Students Emotional Self-Efficacy in Chemistry-SESEC

However, it did not delete items since all items were high loaded (see Table 1).

1. Performing reliability analysis by the Split half method:

Basically, internal reliability determines whether the questionnaire is homogeneous, i.e., whether all items test the same content area. Therefore, at this stage the Cronbach’s alpha values were tested for the five factors within their items.

1. Revisions of Cronbach’s alpha values by changing items or deleting low-loaded items according to our subjective perception:

Cronbach’s alpha values were re-examined after deleting low-loaded items whose omission improved the Cronbach’s alpha values of the factors (Appendix D, where the final items and the reliability values are associated with the relevant factors, and according to the numbering in original questionnaire).

3.1 Teachers’ self-efficacy in teaching with DI in heterogeneous classes

The hypothesis of the research in this context was that the sense of the self-efficacy of the teachers after activating the CPKs will be statistically significantly higher than before the activation. This hypothesis was confirmed. A possible explanation for these findings, according to Suprahyoid and his colleagues (Suprayogi et al., 2017), lies in the fact that a connection exists between DI implementation and the teachers’ sense of self-efficacy. The teachers’ experience in implementing personalized instruction in chemistry high-school classes contributed to their practical skills and their ability to reach all students in a heterogeneous chemistry class (Richards, 2008). As a result, it contributed to their teaching strategies and addressed their need for a higher quality of learning environments and interactions with students (Tschannen-Moran et al., 2006; Zee & Koomen, 2016).

We believe that teachers’ experience with CPKs was a challenging task, and when they experienced success in this challenge in the classroom among their students, their sense of self-efficacy was strengthened. The pedagogical activities and the combining of diverse teaching strategies and methods of the DI has assisted them in dealing with their students’ misconceptions. In addition, it added to the teachers’ toolbox, and exposed them to tools available at their disposal, for implementation in classrooms, and for dealing with the heterogeneity and differences between students. This addressed a main need in the field, due to the lack of available tools to deal with diversity in their classroom (Spektor-Levy & Yifrach, 2019), in addition to the lack of professional support and development that should guide them towards this confrontation, according to (Benny & Blonder, 2018). Furthermore, Suprayogi and his colleagues (Suprayogi et al., 2017) found that 39 % of the variation in the extent to which teachers apply DI in the classroom is related to the variables of teachers’ self-efficacy and class size. Support for this can be found in the current study. We believe that the type, structure, and operating mechanism of the tasks of the CPKs for DI, which the teachers used in their classrooms, addressed this difficulty (Easa & Blonder, 2022). In this way, the students worked in small groups, according to their diagnosed misconceptions. This way of working turned the entire class into smaller teaching centers consisting of 5–6 students at the most (Thakur, 2014), as an accepted way of classroom management in teaching chemistry and science in general. This feature helped the teachers feel more confident in implementing differentiated instruction, in meeting the needs of the students, and it even increased their sense of self-efficacy to use the kits, to improve their teaching activities, and adapt it to diverse learners in the class (Summers & Falco, 2018).

Another possible explanation for the increase in the teachers’ sense of self-efficacy from another point of view involves the use of the CPKs for DI, which consist of diverse pedagogical activities involving technologies, active individual and group learning, to contribute to understanding the concepts and the students’ achievements (Bennett et al., 2007). The result, which improved the students’ performance and their experiences of success during the implementation of the CPKs, led to a decrease in the degree of difficulty in the classrooms, and as a result, the teachers’ sense of self-efficacy increased (Avramidis et al., 2000).

The sense of self-efficacy is a factor that affects teachers’ teaching practices (Maeng & Bell, 2015) and can also predict teachers’ application of DI in the classroom, as Ramli and Nurahimah (2020) found in their study. We hypothesize that repeated and multiple experiences in implementing the CPKs for DI in chemistry classrooms may provide teachers with experience in DI practices, generate more successful experiences in teaching, and more self-confidence in their ability to teach using this pedagogy. In this way, their sense of self-efficacy will rise and lead to openness and to developing a high level of willingness to apply it (Evers et al., 2002).

3.2 Teachers’ attitudes towards DI in heterogenous classes

The hypothesis of the research in this context was that teachers’ positive attitudes towards DI in heterogenous classes would be statistically significantly higher after activating CPKs than before it. The results confirmed the hypothesis.

A possible explanation for this finding lies in the study of Kopmann and Zeinz (2016), who found a strong positive correlation between teachers’ attitudes and the implementation of inclusive and heterogeneous methods and practices. Teachers’ experience with the CPKs with their students had a positive effect on their attitudes, probably because the teaching methods and materials as well as the pedagogical activities in the kits were found to be suitable for them. This in accordance with the findings of Lambe and Bones (2006), who found that sometimes the negative attitudes of teachers can result from inappropriate teaching methods and materials. Additionally, a higher sense of teachers’ self-efficacy is more likely to indicate more positive attitudes towards science (Rachmatullah et al., 2022).

Furthermore, we believe that implementing the CPKs in classrooms increased teachers’ experience in teaching varied lessons and in using adapted instructions regularly. Thus, their attitudes became more positive towards teaching and regarding their ability to teach diverse students (Konstantinou-Katzi et al., 2013). Therefore, their positive attitudes towards heterogeneity in their classes following the implementation of the CPKs were higher (van Steen &Wilson, 2020). Implementing the CPKs in classrooms exposed the teachers to the availability of effective pedagogical tools to deal with students’ misconceptions and provided them with more effective teaching strategies and diverse learning environments (Winzer & Mazurek, 2011), therefore, their attitudes improved.

As described above, activation of the CPKs affected the teachers’ sense of self-efficacy, this might have influenced their attitudes as well. Support for this can be found in several studies (Hosford & O’Sullivan, 2016), which claim that to cultivate positive attitudes, teachers also need to believe in themselves to be able to use inclusive strategies. In other words, teachers’ attitudes towards inclusive teaching in the classroom are positively influenced by their sense of self-efficacy as an experienced teacher. Furthermore, it is possible to understand the importance of professional development for teachers for their practice and for implementing DI in the classrooms. According to Hartwig and Swab, as well as according to the model for developing teacher knowledge (Hartwig & Schwabe, 2018), attitudes are a mediating factor between teacher training and implementing DI in the classroom. Therefore, we suggest that implementing DI can greatly contribute if effort is invested in the training and guidance of teachers. The application of the CPKs will expand the teachers’ toolbox, leading to an improvement in their attitudes.

3.3 Students’ self-efficacy within pedagogical involvement regarding DI

The research hypothesis was that the students’ sense of self-efficacy involved in using the DI approach would be significantly higher than that of students not involved. However, the findings suggest that the sense of self-efficacy for chemistry students who were involved in DI pedagogy is statistically significantly lower, than the sense of self-efficacy of those who were not involved in DI pedagogy after experiencing the CPKs. That is, the hypothesis was refuted.

We believe that the students cognitively understood the point view of DI, and its benefits (Van Aalderen-Smeets et al., 2012). However, a possible explanation for the findings depends on the theory of causal attribution. Attributions are one type of clue that students use to assess their own efficacy. Attribution factors such as the effort invested, the tasks’ estimation difficulty or luck affect performance indirectly through self-efficacy (Bandura, 1986). We believe that students who were provided with explanations about the pedagogy of DI (its meaning, goals, benefits, and impacts) and experienced success in understanding the chemical concepts and content they had previously struggled with might attributed their success to the DI pedagogy, rather than to their own abilities. For them, they have succeeded because the CPKs that implement the DI approach were tailored to their needs and helped them to understand chemistry and not due to their own abilities. Therefore, their sense of self-efficacy did not increase after experiencing the CPKs.

3.4 Students’ attitudes within pedagogical involvement regarding DI

The research hypothesis in this context was that students who were involved in the pedagogy of DI would have significantly higher positive attitudes than those who were not involved. The research findings were not in line with the hypothesis and no significant differences between the two research groups regarding their attitudes toward chemistry were reported after activating the CPKs. That is, the attitudes of all students, those involved in the DI pedagogy and those not involved, increased following the activation. Therefore, the hypothesis was refuted.

We believe that when teachers explained the DI approach to the experimental group regarding its purpose and effects on students’ learning and performance, even though they cognitively understood the explanation, it did not make them become more involved in learning and therefore their attitudes were not affected. Attitudes are a combination of thoughts, affects, and behaviors (Hacieminoglu, 2016; Montes et al., 2018). Attitudes are directly linked to academic achievement and are a predictor of behavior (Najdi, 2018). The teachers’ explanation probably was not enough for the students to fully be pedagogically involved. Therefore, students did not become more involved in their learning, they did not really feel responsible for it, they did not become part of the decision-making in the teaching and learning process (Newmann, 1992), and their interest in understanding the material and concepts learned was not very different from that of the control group. As a result, their attitudes were not more positive. Like Abdous (2019), we believe that students’ level of involvement in learning and teaching promotes their motivation and attitudes toward the content being taught. The activation of CPK activities in the classroom led to a high level of interactions between teachers and students and between the students themselves, which positively affected the extent of their involvement in learning, of motivation and consequently, of attitudes for both study groups (Lee & Hung, 2012). Furthermore, we believe that the implementation of the CPKs in chemistry high school, after participating in an appropriate professional training can be a significant support for teachers for teaching in a heterogeneous class in terms of attitudes and beliefs.

In summary, the teachers’ and students’ (SE-AT) DI questionnaires were found to be valid and reliable tools. These tools examined five factors concerning the students’ and teachers’ attitudes and self-efficacy regarding learning or teaching chemistry by differentiated instruction. Given the need to provide suitable teaching to all, this innovative tool is important for determining DI’s impact and effectiveness.