We developed a biosocial life-course conceptual approach to investigate maternal and household predictors of secondary school dropout, and to ascertain whether the consequences of dropout differ between girls and boys. We analysed longitudinal biomedical data on 648 mother-child dyads from rural Maharashtra, India. Both maternal (low education, early marriage age, shorter pregnancy duration) and household (low paternal education, low socio-economic status) traits independently predicted dropout. Poor child growth and educational trajectories also predicted dropout, mediating the association of only maternal education. Some girls married despite completing secondary education, suggesting the value of education may be subordinated to the marriage market.