Emerging research suggests that children's physical health may account for some of the variability in developmental competencies at school entry, which are the cognitive, learning, and behavioral skills necessary for long-term academic achievement. Most studies on children's health find that neonatal risks, like low birth weight and premature birth, impair children's early functioning, but little is known about other domains of children's health, like global health or acute and chronic conditions, which may be associated with functioning at school entry. Moreover, it is unclear what role physical health may play in children's access to and engagement in home and early childhood education center-based learning contexts, which may function as pathways linking early health disparities with later development. This dissertation tested direct associations between a range of childhood health problems and school readiness skills at kindergarten entry, as well as indirect and interacted associations with early learning contexts. Given the well-established socioeconomic gradient in both health and development, analyses also explored whether associations linking health and development were conditional on family socioeconomic status. Data were drawn from the nationally representative Early Childhood Longitudinal Study (Birth Cohort; N = 5,900), which follows a cohort of children born in 2001 from infancy through kindergarten entry. Linear regressions and path analyses revealed that four of five health conditions were associated with lower school readiness skills, most consistently in the domains of cognitive and learning skills. Neonatal risks, poor health, and hospitalization functioned directly to predict lower cognitive and learning skills, where as asthma diagnosis predicted heightened learning skills. Only poor health functioned indirectly through more restricted home learning activities. Children's time in ECE functioned in a compensatory role to attenuate associations between hospitalization and lower school readiness skills. Across all models, there was no evidence that measured associations varied across the family socioeconomic spectrum. Findings highlight the importance of interdisciplinary research on child well-being and draw attention to potential avenues for prevention and intervention. (author abstract)