There is compelling evidence that high-quality early childhood education and care (ECEC) programs can act to narrow achievements gaps attributed to family socioeconomic status (SES). The everyday ECEC market, however, does not appear to deliver these significant gains. Two reasons for this pattern, recently identified in Australia, are relatively low levels of Instructional Support quality and SES gradients for the availability of ECEC programs and quality. This study addresses a significant gap: exactly how much do ECEC programs contribute to children’s cognitive and academic development.This study uses data from a representative sample of 2494 children attending everyday ECEC programs over a three year period. Children enter the study at age three and four (M = 43 months, SD = 7 months). Linear growth models (LGM) demonstrate small positive effects for early Instructional Support on children’s cognitive development. The effects however are small and constant across the sample. Children from low SES backgrounds are almost 10 months behind their more advantaged peers at entry to school. Children with below average cognitive development trajectories score more than 1.6 standard deviations lower on all NAPLAN outcomes in grade three.This study makes important contributions to the knowledge about the level of quality in everyday ECEC programs, and the effect ECEC programs have on children’s cognitive development and later school achievement. Options for improvement in quality related to Instructional Support will be discussed as will the potential to increase the effect ECEC programs have on children’s cognitive development outcomes.