Student diversity in the classroom represents a significant profes-sional challenge for pre-service teachers. The goal of this study is to explore how mentor teachers support pre-service teachers in addressing student diversity during their practicum. Eight pre- service teachers and their six mentor teachers were participants in a multi-sited ethnographic study conducted in the Czech Republic. Data collection took place at lower secondary schools and in a teacher education faculty. We identified seven strategies that mentor teachers use and we explain how these strategies shape pre-service teachers’ thinking and behaviour related to student diversity. The overall outcome presents a contradiction: when men-tor teachers model practice, they tend to emphasise individuality; however, when they provide feedback, they tend to emphasise universality. Importantly, we proved that feedback shaped pre- service teachers more than modelling. From the discussion of our findings, we derive six indicators that determine quality mentoring regarding addressing student diversity.