Classrooms in rather homogeneous post-socialist countries have become more diverse as the number of pupils with special education needs and disabilities (SEND) have increased. Furthermore, differences among students spring from other diverse individual needs based on academic strengths, interests, learning profiles, readiness, etc. This can represent a challenge for teachers who express frustration with attempting to successfully deal with student diversity (Tomlinson, et al., 1998). Working with this diversity may require specific skills of pre-service teachers (e.g., differentiated instruction, Smale-Jacobse et. al, 2019) which can be developed during their practicum, often considered a key element of teacher education (e.g., Korthagen et al., 2001). The goal of this substantive paper is to explore how pre-service teachers tackle student diversity during their practicum and how this is facilitated by their participation in university courses. The paper draws on a large data corpus composed of 120 observed lessons among eight student-teachers teaching directly in three lower-secondary schools, 90 audio recordings of post-lesson interviews between student-teachers and their six mentors, and 30 semi-structured interviews conducted with pre-service teachers and their mentors. Further data from four general education courses at a university includes the participant observations of 40 on-campus lessons as well as 24 entries in reflective diaries of their practicum experiences and 27 other tasks submitted in seminars. Pre-service teachers’ beliefs and practices related to their practicum at lower-secondary schools are mainly focused on students with SEND or students without formalized support measures who are “conspicuous” in terms of their degree of disruption, talent or pace, etc. For these students, pre-service teachers often use elaborated strategies. As a result, responding to the individual needs of “average” students is usually suppressed. Relatedly, pre-service teachers lack competence in using different grouping strategies (enabling attendance to the individual needs of all students) as well as confidence in extracting potential from situations of individualization for teaching the whole class. This could be interlinked with university curricula where pre-service teachers learn about teaching strategies for underachievers or overachievers; thus, in terms of differentiated instruction, these two groups are separated, and students who are “in the middle” remain left behind. While short-term quantitative research on pre-service teacher attitudes and beliefs on diversity prevail (Sleeter & Owuor, 2011), ethnographic research triangulating diverse data on their practices in heterogeneous classrooms is scarce. Furthermore, the paper expands the field of teacher education ethnography as it interconnects data from different settings. Previous studies confining their focus mainly to the university setting (Mills & Ballantyne, 2016) did not triangulate diverse data collected across different settings with the same rigour (Obrovská & Tůma, 2020) and relied heavily on self-reported data from pre-service teachers. In exploring the ways in which pre-service teachers dealing with diversity during their practicum is facilitated by their participation in university courses, we are inspired by multi-sited ethnography (Marcus, 1995), which has not often been utilized in educational research (Pierides, 2010).