Research Findings: The present study examined patterns of executive function (EF) development among socio-demographically diverse children in kindergarten, first grade, and second grade. Using nationally representative data from the Early Childhood Longitudinal Study Kindergarten Cohort: 2011, we estimated children's growth in working memory and cognitive flexibility across four socio-demographic profiles of children, which we identified using cluster analysis. We then explored the extent to which child, family, and classroom characteristics explained heterogeneity in EF development across the child profiles. Results indicate that low-SES and Hispanic dual-language learning children with immigrant parents entered kindergarten with the lowest average EF skills but then made remarkable EF gains. This catch-up was largely explained by a negative association between initial EF skills and subsequent EF gains. However, low-SES, non-DLL Black and Hispanic children had similarly low initial EF skills, but did not exhibit the same pattern of catch-up, in part due to their reduced likelihood of enjoying positive relationships with their teachers. Practice or Policy: The findings add to the growing literature on heterogeneity in EF development and demonstrate the need to assist teachers in forming positive relationships with all children in socio-demographically diverse classrooms.