The Study on the effective use of early childhood education and care (ECEC) in preventing early school leaving (ESL) aimed to collect evidence on how equitable and high-quality early child education and care can influence the performance of children in the subsequent stages of education and possibly contribute to the prevention of early school leaving. In order to achieve this, the following steps were undertaken: The research review stage focused on synthesising the already existing evidence on the links between quality of ECEC and children's learning progress. This allowed major gaps in existing research to be identified and directions for future studies to be provided. The synthesis included an overview of literature and policy documents in the languages of 34 European countries. The policy mapping stage helped to update policy information available from the previous studies and to make an assessment on the quality of ECEC and on the balance and continuity between the earliest and the later stages in education in the analysed European countries. It also helped in selecting the countries for case study analysis, taking into consideration the principles of diversity and representativeness. The case study analysis was carried out in Austria, Belgium, Croatia, Finland, France, Italy, Lithuania, Spain, Sweden and the UK. The case studies analysed the influence of ECEC policies on the learning of children in a particular country context. They complemented country-specific evidence collected during the research review stage and tried to assess how declared national policies are implemented in practice. The synthesis of the research review, case studies and policy mapping reports helped to revisit the role of early childhood education and care in children's development in a new light by bringing together the research findings from different levels of education, different disciplines, and different country contexts in this report and identifying the areas that need to be considered in further research. (author abstract)