In this study I hypothesize a larger penalty of obesity on teacher-assessed academic performance for white girls in English, where femininity is privileged, than in math, where stereotypical femininity is perceived to be a detriment. This pattern of associations would be expected if obesity largely influences academic performance through social pathways, such as discrimination and stigma. In the Fragile Families and Child Wellbeing Study (age ~9) and the National Longitudinal Study of Youth 1997 (age ~18), I find obesity to be associated with a penalty on academic performance among white girls in English but not in math, while no association is found in either subject for white boys or for black students net of controls. Findings suggest that the relationship between obesity and academic performance may result largely from how educational institutions interact differently with bodies of different sizes rather than primarily via constraints on physical health.