This study takes a life course approach to adolescent academic and health-related behavior. Researchers have often studied academic achievement and substance use as unrelated, static, and de-contextualized phenomena. Applying latent growth curve modeling to a sample of 2,651 high school freshmen and sophomores in California and Wisconsin (1987-1990), this study treats achievement and substance use as dynamic trajectories, inter-related to each other, and influenced by proximate and structural contexts. In general, achievement is high at the start of high school and then declines. This downward trend is driven by male non-athletes. Substance use is initially low and then increases, with boys driving this increase. Finally, academic and health-related trajectories are most related among athletes, who experience long-term academic consequences from risky health-related behavior. Overall, gender-athletic status can serve as either protective or risk factor, depending on the behavior and the temporal perspective.