This article examines the potential benefits and risks of participation in five types of extracurricular activities: prosocial (church and volunteer activities), team sports, school involvement (pep club, student council), performing arts (drama, marching band), and academic clubs (science club, foreign language club). The study, based on data from the Michigan Study of Adolescent Life Transitions (MSALT), involved 1,259 mostly European American adolescents. The findings suggest that involvement in prosocial activities is linked to positive educational outcomes and low rates of risky behaviors, while participation in team sports is associated with positive educational outcomes but also high rates of alcohol use. The study also explores the role of peer associations and activity-based identity formation as possible mediators of these associations. The research highlights the importance of constructive, organized activities for adolescents, as they provide opportunities to develop social skills, community involvement, and a sense of identity. However, it also notes that relaxed leisure may have less beneficial developmental outcomes. The study found that participation in various forms of constructive leisure is associated with positive developmental outcomes such as higher GPA, better school engagement, and increased college attendance. In contrast, involvement in team sports was linked to increased rates of school deviance. The study also found that participation in sports is associated with both positive and potentially negative consequences. While sports participation is linked to increased likelihood of college attendance and school attachment, it is also linked to increased alcohol use. The study suggests that the protective effects of sports participation may be due to the influence of peer groups and identity formation. Overall, the study concludes that participation in prosocial activities is most consistently associated with positive developmental outcomes, while participation in team sports is associated with both positive and negative outcomes. The study also highlights the importance of peer group and identity formation in explaining the associations between activity participation and adolescent development.This article examines the potential benefits and risks of participation in five types of extracurricular activities: prosocial (church and volunteer activities), team sports, school involvement (pep club, student council), performing arts (drama, marching band), and academic clubs (science club, foreign language club). The study, based on data from the Michigan Study of Adolescent Life Transitions (MSALT), involved 1,259 mostly European American adolescents. The findings suggest that involvement in prosocial activities is linked to positive educational outcomes and low rates of risky behaviors, while participation in team sports is associated with positive educational outcomes but also high rates of alcohol use. The study also explores the role of peer associations and activity-based identity formation as possible mediators of these associations. The research highlights the importance of constructive, organized activities for adolescents, as they provide opportunities to develop social skills, community involvement, and a sense of identity. However, it also notes that relaxed leisure may have less beneficial developmental outcomes. The study found that participation in various forms of constructive leisure is associated with positive developmental outcomes such as higher GPA, better school engagement, and increased college attendance. In contrast, involvement in team sports was linked to increased rates of school deviance. The study also found that participation in sports is associated with both positive and potentially negative consequences. While sports participation is linked to increased likelihood of college attendance and school attachment, it is also linked to increased alcohol use. The study suggests that the protective effects of sports participation may be due to the influence of peer groups and identity formation. Overall, the study concludes that participation in prosocial activities is most consistently associated with positive developmental outcomes, while participation in team sports is associated with both positive and negative outcomes. The study also highlights the importance of peer group and identity formation in explaining the associations between activity participation and adolescent development.