It has been argued that high school sports participation increases motivation and teaches teamwork and self-discipline. While several studies have shown that students who participate in athletic activities perform better in school than those who do not, it is not clear whether this association is a result of positive academic spillovers, or due to the influence of unobservables. Using data from the National Longitudinal Study of Adolescent Health and a variety of statistical techniques designed to distinguish between these hypotheses, we examine the effect of sports participation on several measures of academic performance. Our results provide only limited evidence that sports participation leads to enhanced academic performance.