The present study examined the degree to which the association between interactive peer play and academic skills was dependent upon the level of classroom quality for a representative sample of culturally and linguistically diverse urban Head Start children (N=304 children across 53 classrooms). Peer play interactions within the classroom were assessed by teacher assistants in the fall of the year; observations of the quality of classroom instructional, emotional, and organizational support were conducted in the middle of the year; and norm-referenced direct assessments of literacy, language, and mathematics skills were administered in the spring. Findings from multilevel models indicated that disruptive and disconnected peer play behaviors early in the preschool year were associated with lower literacy and language skills regardless of classroom quality. However, interactive peer play early in the year was associated with higher mathematics outcomes when children were enrolled in classrooms characterized by high instructional support. (author abstract)