Despite schooling gains over the last two decades, Mexican-origin adults complete fewer years of schooling than adults from other ethnic backgrounds. Explanations emphasizing network resources suggest Mexican-origin adolescents have social ties that are more likely to be “closed” from adults with experience in higher education—and this, in turn, inhibits the transition to college. In this study, we draw on unusual network data measuring characteristics of students' peers and friends, as well as the socioeconomic background of peers' and friends' parents. We demonstrate that Mexican-origin adolescents are much less likely to have friends whose parents have college educations. 83% of non-Hispanic Asian students and 72% of non-Hispanic white students have nominated friends with college-educated mothers; about half of Mexican-origin students do. These patterns are the result of socioeconomic segregation in social networks both across and within schools. Within schools, we observe that the educational background of friends is predictive of schooling outcomes for non-Mexican students. We find evidence that this network resource shapes non-Mexican students’ educational expectations in high school and longer-run completed schooling as adults more so than it shapes the outcomes among Mexican-origin students.