A large body of research demonstrates a positive association between maternal education and child development. What is not yet known, however, is whether and to what extent the association between mothers' education levels and their young children's outcomes varies across developmental stage (infancy, toddlerhood, or preschool) and child outcome domain (cognitive, social-emotional, and health) prior to school entry. Using a national sample of low-income mothers (n [is approximately equal to] 3,200), the present study finds that maternal education increases during children's earliest developmental stages are more strongly associated with children's outcomes than education increases later on. The directions of those associations vary, however, across domains, such that earlier increases in maternal education level are associated with increased child language and literacy scores and healthier child BMI, but also with elevated hyperactivity and conduct problems relative to no increases at all. These diverging associations by developmental domain are observable as early as preschool and heighten in magnitude by kindergarten entry. We discuss results to inform the targeting and design of two-generation education programs aimed at jointly improving the lives of low-income children and their parents. (author abstract)