This dissertation consists of three-related research papers that investigate the relations between core features of non-parental childcare settings —quality, quantity, and type—and children's school readiness. My first paper is a descriptive study of the role that childcare quality might play in narrowing school readiness gaps. Drawing on data from the ECLS--B longitudinal study, I estimate gaps between low--SES and high--SES children on early academic and socio-behavioral outcomes, measured at preschool age and kindergarten entry. I decompose SES gaps to estimate how much the disparity in the quality of childcare environments contribute to SES gradients in child outcomes. Then, I identify predictors of participation in higher-quality childcare services at preschool age. My second dissertation paper explores the impact of the timing (duration) and sequence of exposure to different childcare arrangements on child outcomes. Based on ECLS--B data and a novel strategy to account for dynamic selection bias—an extension of the Inverse Probability of Treatment Weights (IPTW), I estimate the differential effect of the age of entry into center-based care and the effect of the cumulative exposure of attending one type of care at the age of 2 and switching to another type at the age of 4 on child outcomes. Next, I examine the extent to which both effects vary by family income and race. Finally, my third dissertation paper evaluates afterschool center-based care programs in kindergarten as a means of supporting children's development during the transition to formal schooling. Using data from the Early Childhood Longitudinal Study--Kindergarten Cohort (ECLS--K) and matching estimators, I examine families' propensity to use afterschool center-based care as well as the causal impact of attending such programs on a child's academic and socio-behavioral outcomes, measured at the end of the kindergarten year. To evaluate the potential of afterschool center-based care programs to reduce the school readiness gap, I explore heterogeneous effects by family income and race.