This multi-sited ethnographic study explores how pre-service teachers (PSTs) address pupil diversity during their practicum at lower secondary schools and how this is facilitated by their participation in university courses. This investigation's focus on diversity is grounded in the concept of differentiated instruction. We found out that university teaching contributes to PSTs having a positive approach towards pupil diversity and that in their practicum PSTs succeed in taking the needs of certain groups of pupils into account in the classroom. However, PSTs take the needs of pupils into account unevenly and tend to homogenise their teaching on their practicum, to which the university curriculum also contributes by not being sufficiently experience-based and not providing a systematic framework for addressing the needs of all pupils in the classroom.