This study explored how discrepancies between parents' and adolescents' educational expectations influenced adolescents' achievement using a nationally representative, longitudinal sample of 14,041 students (14 years old at baseline). "Actual" discrepancies (i.e., those between parents' and adolescents' actual educational expectations) and "perceived" discrepancies (i.e., those between adolescents' perceptions of their parents' educational expectations and adolescents' own) were examined. Achievement was higher when parents "actually" held higher expectations than adolescents held or when adolescents "perceived" that their parents' expectations were lower than their own. In contrast, achievement was lower when parents "actually" held lower expectations than adolescents held or when adolescents "believed" that their parents' expectations exceeded their own. Implications for identifying adolescents at risk and promoting adaptive parent-child educational expectations are discussed.