Today’s world has become more and more diverse, and classrooms are a clear reflection of this reality. Despite the fact that school systems worldwide have responded to student heterogeneity by establishing, for example, tracking or streaming (Dupriez, Dumay, & Vause, 2008), teachers still report that the heterogeneity of the student population is substantial and continuously increasing (Dixon, Yssel, McConnell, & Hardin, 2014). Heterogeneity is not limited to performance, but encompasses cultural background, language competence, learning styles, and motivation (Valiandes, 2015). Teachers’ ability to effectively instruct “heterogeneous classes of pupils from diverse social and cultural backgrounds and with a wide range of abilities and needs” (European Trade Union Committee for Education, 2008, p.20) is considered as key pedagogical skill enclosed under the core competences stated by the European Commission (Caena, 2011), and thus, a challenge for educational systems across country boundaries.

In order to address students’ various needs, teachers are required to differentiate their instruction. Differentiated instruction (DI) has historically been an issue throughout the last decades (Klafki & Stöcker, 1976). DI is conceptualized as a toolbox of instructional practices which teachers can appropriately cater to students’ prerequisites and ensure successful learning inside the heterogeneous classroom (Pozas & Schneider, under review). Despite the extensive literature available on DI (Schumm & Vaughn, 1991; Smit & Humpert, 2012; Tomlinson, 2014; Wischer & Trautmann, 2012), existing DI frameworks tend to describe single exemplary DI practices, widely lack an empirical approach, and thus, provide little help to classroom teachers. In addition, none of these theoretical frameworks are appropriate for answering teachers’ practical questions regarding the concrete options they have at hand for differentiating instruction. In order to facilitate teachers’ instructional decisions, Pozas and Schneider (under review) propose a taxonomy of DI practices attempting to bridge the gap between educational theory and everyday instructional practice.

The taxonomy organizes DI practices into six categories:

(I) Tiered assignments: qualitative and/or quantitative variation of materials and tasks according to challenge level, complexity, outcome, process, product, and/or resources.

(II) Intentional composition of student working groups: establishing decidedly homogeneous or heterogeneous subgroups based on performance, readiness, interests, etc.

(III) Tutoring systems within the learning group: high ability students take up the role of teacher assistants and tutor low ability students. These roles may persist for a long term.

(IV) Staggered nonverbal learning aids as a scaffolding practice: carefully and purposely designed series of learning aids that range in complexity level. The learning aids must only contain the minimal information necessary for a student to overcome an obstacle. If they still are unable to deal with the task, a second aid with additional information and guidance is provided.

(V) Mastery learning: all instructional practices which ensure that all students achieve at least minimum standards (in combination with higher standards for the more advanced students). This involves close monitoring of students´ learning progress.

(VI) Open education / granting autonomy to students: Students are responsible for their own learning process and may autonomously decide on materials to work upon. Examples of such practices include: student choice of tasks, station work, project-based learning, portfolios, etc.

Following this taxonomy, our paper reports two studies using a qualitative and quantitative approach to answer the research questions:

1. Which practices are applied as a mean for teachers to differentiate their instruction, how often do they apply such practices, and what intentions do they pursue?
2. Does the use of DI practices vary across school tracks?

By exploring teachers’ use of DI practices from both a qualitative and quantitative approach, we aim to gain deeper insight into teachers’ preparation and actual in-class behavior, as well as, providing empirical evidence.

To examine both research questions, two studies were conducted: In the qualitative study, regional (area of Trier, Rhineland-Palatinate, Germany) teachers to describe their differentiated instruction implemented in their everyday lesson preparation and teaching. In order to examine the taxonomy’s validity, a qualitative approach was followed. In this study, 24 German and/or English teachers working in different school tracks (school with different courses of education, comprehensive school, and advanced secondary school) within the German school system were interviewed. The semi-structured interviews were based on the DI taxonomy described above and asked teachers about their implementation of DI practices in their everyday classroom teaching. The interviews were analyzed by means of qualitative content analysis (Mayring, 1990). In a deductive approach and on the basis of current literature on DI (e.g. Smit & Humpert, 2012; Tomlinson, 2014), the taxonomy’s categories (I-VI) were used as one dimension of clustering DI practices. Inside these categories, teachers reported on the frequency with which they applied the respective DI practices and on the intentions behind the application. Inside the taxonomy’s categories, reported intentions were grouped inductively. The quantitative study examines teachers’ implementation of within-class DI practices using data from the National Educational Panel Study (NEPS). The NEPS is a longitudinal study on education conducted nationally in Germany and follows a multi-cohort sequence design that aims to examine educational processes and outcomes in different developmental stages of a life course (Blossfeld, Roßbach, & von Maurice, 2011). The present study examines Cohort 3 consisting of 5286 ninth grade German (Nᴳ) and Math (Nᴹ) teachers (Nᴳ=2439/Nᴹ=2847), which is stratified according to school track within the German school system: general secondary school (Nᴳ=326/Nᴹ=302), school with different courses of education (Nᴳ=298/Nᴹ=352), intermediate secondary school (Nᴳ=585/Nᴹ=706), comprehensive school (Nᴳ=189/ Nᴹ=223), and advanced secondary school (Nᴳ=1041/Nᴹ=1264). Mixed analyses of variance were conducted using teachers’ responses to within-class differentiation related questions concerning how they conduct, plan, and organize lessons.

The qualitative study revealed that all single DI practices named by the teachers could indeed be clustered into the categories of the DI taxonomy introduced by Pozas and Schneider (under review). Moreover, the interviews showed that certain practices (e.g. tiered assignments) were used more frequently, whereas other categories were rarely used in class (e.g. tutoring systems). Furthermore, differences between teachers’ repertoires of DI practices could be identified: teachers working in advanced secondary schools implement less DI practices into their teaching; in contrast, teachers in schools with different courses of education reported that they use a wider range of DI practices. In terms of intentions, several distinct types of intentions were identified, including for instance fostering of weak learners, fostering of strong learners, fostering of autonomous learning, fostering of social competences, and increase of student activity. In addition, results on teachers’ intentions for the use of DI reveal both, differences and congruencies across school tracks. Results from mixed ANOVA indicated significant variations across DI practices: tiered assignments are by far the most used DI practice by German and Math teachers. For intentional within-class student grouping, data shows that across both subjects, teachers form heterogeneous ability groups rather than homogeneous ability groups. In addition, results indicated significant variations of DI practices across school tracks in both subjects, for example: a) comprehensive school German teachers commonly use tutoring systems, whereas in general secondary school, this approach is mostly implemented by Math teachers, and b) open teaching is hardly practiced in both subjects. Overall, results from both studies highlight a tendency in regards to teachers’ use of DI in subjects such as German, English, and Math: it’s without a doubt that teachers make use of DI. Nonetheless, both studies suggest that DI occurs in less quantity than required for effective management of student heterogeneity.

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