Fourth-grade children's peer groups were identified using the Social Cognitive Mapping (SCM) procedure. Children (N = 143) and caregivers then participated in interviews in which they provided information used to construct a measure of social network (intergenerational) closure, defined as the extent to which meaningful social relationships existed between children and their friends' parents and among parents whose children were friends. Higher levels of social network closure were linked with higher achievement test scores and lower levels of parent-reported externalizing behavior. Among European American children only, higher levels of social network closure also were linked with higher levels of teacher-rated social competence. Higher levels of closure were associated with more externalizing behavior (as reported by parents and teachers) among African American children, but less externalizing behavior among European American children. Negative associations between closure and internalizing behaviors were strongest among girls who were bused from a different neighborhood to attend the target school.