Research shows that peer relationships are associated with students' school adjustment. However, the importance of advantageous and disadvantageous factors for students' educational outcomes may vary by socioeconomic positioning. Drawing on sociometric and register data from a nationally representative sample of Swedish youth (n = 4996, girls 50%; migration background 19%), this study asks if family socioeconomic status moderates associations between youth's peer relationships and their subsequent educational outcomes. Based on preregistered analyses, associations that peer acceptance and rejection at age 14-15 years share with school grades at [approximately]16 years and completion of upper secondary school at [approximately]20 years were tested. The findings showed that positive and adverse peer relationships are most consequential for the educational outcomes of socioeconomically disadvantaged youth.