Participation in sport and exercise has been linked to enhanced academic performance, and though girls' participation in sport is known to decline during adolescence, girls continue to outperform boys academically at school in many Western nations. Drawing on evidence that social identities are linked to a range of health and cognitive benefits, we investigated the potential positive effects of shared group memberships associated with team sports and other extracurricular group memberships on the cognitive performance of a nationally representative sample of adolescents in Ireland. Using the Growing up in Ireland Survey (GUI), we explore the impact of reported participation in group activities on the cognitive performance of 13 year old boys and girls (N = 7525) over and above exercise participation. The findings indicate significant interaction between gender and social group membership on various indicators of cognitive performance, while controlling for exercise. Further, the findings indicate that while exercise underlies the positive effects of group membership on cognitive performance for boys, this is not the case for girls. The theoretical and policy implications of these findings are discussed.