A great deal of recent research has employed instrumental variables to estimate the effect of participation in athletics on academic or labor market outcomes, finding evidence of small positive effects from participation. This research proposes several theories of how participation affects success but cannot distinguish between them. I ask a fundamentally different question, whether an athlete performs better or worse, academically, during the season in which they participate in sports, focusing on the time allocation theory of participation. Time spent on sports may substitute from time on academics or negative leisure activities, causing academic performance to improve or decline in-season, respectively. This paper finds a small negative and significant in-season effect on academic performance for varsity athletes and a small positive and significant in-season effect on academic performance for junior varsity (JV) athletes. Decreases in in-season grade point average (GPA) for varsity athletes occur through a decline in performance in English and history courses, while increases in in-season GPA for JV athletes operate through an improvement in math and science courses. Results are robust to controlling for various measures of course ease across semesters. The relatively small in-season effects suggest that estimates of the effects of participation in the rest of the literature operate primarily through mechanisms other than time allocation.