The mandated Early Years Learning Framework for Australia (EYLF) has guided early childhood education and care (ECEC) since 2009. The EYLF is intended to support improved learning and development outcomes for all children within a nationally consistent regulatory system. Since the implementation of the EYLF, the quality ratings of ECEC services have improved in every Australian jurisdiction. However, the absence of detailed child ECEC participation data has been an obstacle to assessing the impact of ECEC service level improvements on child learning outcomes. It is therefore reasonable to ask whether the implementation of the EYLF is associated with changes in child outcomes at a population level. We examined child-level data from five, three-yearly rounds of the Australian Early Development Census (AEDC) collected in the first year of formal education from 2009 to 2021, the same period over which improvements in ECEC quality standards have been documented. In all five developmental domains assessed by the AEDC, scores of children attending any form of ECEC were higher on average over every round of data collection. However, these group average differences remained stable from 2009 to 2021. Improvements in aspects of quality underpinning the EYLF and national regulatory standards may not be sufficient to reduce levels of developmental vulnerability so as to alter the developmental trajectories assessed by the AEDC in a meaningful way in the population.