Ethnic identity plays a key role in the normative development of children and adolescents, and efforts to provide a positive and safe environment for ethnic identity benefit from an understanding of its context-dependency. Following the social identity perspective, we add to research on ethnic identity by considering the role of the classroom context and by conceptualizing ethnic identity in terms of two key dimensions. Specifically, the present study aims to investigate the role of the classroom context for ethnic private regard (positive ethnic self-feelings) and for the under-researched construct of ethnic introjection (subjective self-group merging). These two dimensions of ethnic identity were examined in 51 Dutch school classes among grade 4–6 students (N= 573; Mage = 10.77, SD = 1.02; 54% girls) of Dutch, Turkish and Moroccan ethnic background. We focused on teachers’ multicultural norms and classmates’ evaluation of the ethnic in-group (peer group norms) in combination with the ethnic class composition. It was found that ethnic introjection was empirically distinct from ethnic private regard, and that the former dimension depended on the classroom context more than the latter. Multicultural teacher norms affected minority preadolescents’ private regard positively, but only when the share of in-group classmates was low. Positive peer group norms of in-group classmates strengthened students’ introjection, while those of out-group classmates lowered it. The findings indicate that ethnic identity research will be enhanced by more fully considering the conceptual and contextual implications of the social identity perspective.