This article examines how network closure among parents affects adolescents’ educational attainment. First, we introduce a distinction between informal closure and school‐based closure. Second, we investigate whether and how the effect of informal and school‐based parental network closure varies across social contexts. Findings from the National Longitudinal Study of Adolescent Health (Add Health) and multilevel models show that parental network closure modestly impacts educational outcomes. Moreover, educational benefits of informal closure in parent networks are contingent on social context. Closure only benefits educational attainment in low‐poverty schools. In high‐poverty schools, informal closure in parent networks lowers educational attainment. The social closure generated in informal connections among parents thereby contributes to the encapsulation of disadvantage in areas of concentrated poverty, which is not the case for school‐based closure.