Differentiated instruction (DI) is put forward as a pedagogical approach to create an inclusive classroom and is considered both a teaching philosophy and a teaching praxis. DI requires that teachers adapt their teaching to students’ interests, readiness and learning profiles by adopting differentiated practices such as flexible grouping and ongoing assessment. However, several studies report implementation challenges for DI practices. Using mixed methods, this study explores to what degree differentiated practices are implemented by primary school teachers in Flanders (Belgium). Data were gathered by means of three different methods, which are compared: teachers’ self-reported questionnaires (N=513), observed classroom practices and recall interviews with 14 teachers. The results reveal that there is not always congruence between the observed and self-reported practices. Moreover, the study seeks to understand what encourages or discourages teachers to implement DI practices. It turns out that concerns about the impact on students and school policy are referred to by teachers as impediments when it comes to adopting differentiated practices in classrooms.