The literature on mother's education and child health casually observes some nonlinearities and also a threshold in the relationship. Even though this nonlinearity or threshold has significant bearing on policy matters such as quality of education, any rigorous attempt to address this issue is missing in the literature. With height for age z‐score as a proxy for long‐run child health capital, regression results reveal that there are significant effects of mother's education on child health if mothers do not continue past primary school. Rather, poor quality of education at the primary level, especially literacy, is argued to have given rise to this threshold. It indicates that greater public investment in improving quality of education at the primary level is essential for maximizing the nonmarket outcomes of girls’ education in developing countries.