EPPE 3-11 is a large study of the developmental trajectories of approximately 2800 children in England from age 3 to 11 years. This report focuses on the primary school phase, particularly Key Stage 2 (ages 7-11). Many children have prospered, leaving Key Stage 2 (at age 11) with confidence and armed with the skills they need to tackle learning in secondary school. However, some children moved onto secondary school with poor skills in key areas or with low self-image and aspiration. The EPPE 3-11 project set out to explain some of the reasons behind these different developmental trajectories.