This study utilized data from the Avon Longitudinal Study of Parents and Children (N = 14,860) to examine whether early-life family income (age 0-5) predicted long-term academic achievement (age 16-18) and to investigate the role of executive function (EF) assessed multiple times across age 7-11 in explaining this association. Task-based EF was a significant mediator between early-life family income and later academic achievement in every model. This mediating pathway persisted when adjusting for a comprehensive panel of covariates including verbal IQ, sex, family income at ages 8 and 18, and early-life temperament. Additionally, teacher-rated and parent-rated EF mediated in some models. Overall, these findings suggest that childhood EF may play an important role in perpetuating income-based educational disparities.