Family background, particular socioeconomic status (SES), is related to children's cognitive, intellectual and social development. The mechanism through which family SES influences children's development is indirect: lower availability of recourse means that children from less advantaged background experience fewer stimulating or enriching experiences. Experimental research has shown that high quality out-of-home experiences for children from less advantaged backgrounds can lift children's developmental outcomes and ameliorate the effect of disadvantage on development. However, low SES families are less likely to have high quality out-of-home experiences available to them: families that select into these programs tend to have more resources and information and therefore face fewer barriers to entry. It is therefore not known if children from less advantaged backgrounds are getting the kind of experiences that ameliorate their risk of poorer outcomes or whether the status-quo provision of early childhood education and care is being shown to ameliorate poor developmental outcomes. This study uses data from a large, longitudinal study of participation in early childhood education and care (ECEC) programs from approximately 2500 children using the Woodcock Johnson III (WJIII) Tests of Cognitive Abilities to measure children's development and the Classroom Assessment Scoring System (CLASS) to measure the interaction quality in the early childhood education and care programs they attend. A weighting methodology is presented to account for the complex, cluster-based sample design so that generalised statements can be made: This study asks: 1. Are high quality programs uniformly distributed amongst communities of all levels of advantage?2. Are high quality programs attended uniformly by children from all levels of advantage?3. Are children for less advantaged backgrounds who attend high quality programs seen to be achieving better outcomes than their peers form similar familial backgrounds? A linear growth model is used to estimate the developmental trajectories of children over three years, conditioned on ECEC quality, ECEC dosage, family background, and child latent characteristics. These findings flag the importance of early intervention: by school entry, children from less advantaged backgrounds are observed in lower quality ECEC programs and are losing ground to their more advantaged peers. High quality ECEC programs, particularly those proximal to school entry and demonstrating high Instructional Support have the capacity to ameliorate disadvantage early and offset growing disparities between children over time.