Using National Longitudinal Study of Adolescent Health (Add Health) data, this research documents the prevalence of the different stepfamily forms in which American adolescents live, examines the family structure pathways through which adolescents traveled to arrive at their current family form, and explores the effects of these pathways on grades, school-related behavior, and college expectations (N = 13,988). Compared to those who have always lived with both biological parents, youth in pathways including divorce/separation or a nonunion birth experience significantly lower academic outcomes, while those whose pathways include parental death do not. Specific effects vary, however, according to the outcome examined. For example, the combination of divorce/separation and movement into the least common of family forms is associated with particularly poor GPA outcomes. Divorce/separation is also more detrimental than nonunion birth for college expectations, particularly when coupled with a transition into a stepfamily based on cohabitation. Divorce/separation and nonunion birth have similar, negative effects on school behavior problems. Overall, results indicate that living in a stepfamily does not benefit youth, and can in some ways disadvantage them, even compared to their peers in single-mother families. This is especially the case if youth transition into a stepfamily following a combination of stressful family experiences. These findings underscore the importance of examining family effects from a longitudinal perspective.