Using a transactional framework, this study explored social relationships in the classroom as mediators of the association between ethnic-racial identity and academic outcomes. Participants were 101 5th graders of diverse backgrounds who completed computer-based questionnaires about their friendships, ethnic-racial identity, and academic engagement. Teachers reported on closeness and conflict in the student-teacher relationship. Relationships in the expected direction were evident between the public regard and centrality dimensions of ethnic-racial identity and social relationships as well as with academic outcomes. Further, path analyses revealed that the relationship between the public regard and cognitive engagement was mediated by student-teacher closeness. Gender differences were evident for pathways to grades; such that for boys’ public regard was indirectly related to their language arts grades through cognitive engagement. The current study highlighted the varied effects of ethnic-racial identity and classroom relationships’ on academic outcomes particularly for boys.