This article examines the relationship between birthweight, adolescent health (general health and psychological distress) and high school completion in Norway, using survey data linked to longitudinal registry data (n = 5,354). The findings show that the positive association between birthweight and high school completion can be attributed to socioeconomic status. General adolescent health is explained by socioeconomic status combined with risk- and protective behavior. Psychological distress is mediated by having a close relationship with family and friends among the most affluent students, but not among the lower-income students. Among the lower-income students it was, instead, absence from school and feeling comfortable in class that mediated the association between psychological distress and high school completion, net of other factors.