The rise of school-based mental health interventions calls for an understanding of how such interventions interact with context as well as analytical tools for examining these interactions. This article explores how learners and teachers in two classrooms for newly-arrived migrant adolescents in Denmark (one urban, highly diverse classroom and one small-town classroom mainly serving youth who had fled armed conflict) experienced and implemented the same teacher-led, classroom-based intervention differently. Based on participant observations and interviews with three teachers and 12 learners, we draw on practice theory to disentangle how the same intervention came to life differently in the two classrooms. First, there were important differences in how teachers and learners in the two classrooms made sense of their participation in the intervention, reflecting the different life situations and psychosocial needs of the learners. Second, local ways of structuring educational practices (weekly schedules, expectations about homework, and different local educational policies) critically shaped intervention experiences and implementation. Third, the possibility of establishing a safe social space during the intervention depended on the stability of existing social relationships and conditions for teachers’ relational work in the classrooms. To aid analyses of how school-based interventions interact with classroom practices, and to help identify ways of consolidating interventions with their contexts, we propose future avenues for examining school-based mental health interventions in context from a social practice perspective.