Using data from the Early Childhood Longitudinal Study-Kindergarten Cohort (N = 13,970), we examined whether two aspects of school-family connections, parental involvement and communication quality, accounted for the association between classroom composition and children's academic and socioemotional functioning following the transition to elementary school. For students with more same-race/ethnic representation in their classrooms, greater classroom race/ethnic diversity promoted more parental involvement, which in turn promoted children's interpersonal skills and reading achievement. Classroom diversity made little difference to parental involvement when students had fewer same-race/ethnic peers in the classroom. Teacher-parent communication quality did not emerge as an explanatory mechanism, and findings did not vary by the race/ethnic match between students and their teachers.