There is a long history of research in the UK and elsewhere showing that children who are born at the end of the academic year tend to have lower educational attainment than children born at the start of the academic year. In England, where the academic year runs from 1 September to 31 August, this means that children born in the summer tend to perform worse than children born in the autumn. There is also growing evidence that the month in which children are born matters for a range of other skills and behaviours as well, such as the likelihood of being assessed as having special educational needs at school, and children’s self-esteem and confidence in their own ability. Why should this matter to policymakers? There are at least two reasons: first, because these differences in educational attainment and other skills and behaviours may affect children’s well-being in the short term; and second, because they may have potentially serious long-term consequences for children’s lives. This report aims to inform the policy debate on this important issue by providing clear evidence on the magnitude of the differences in outcomes between children and adults born at the start and end of the academic year in England and, more importantly, offering new insight into the drivers of these differences. This is vital in order to determine the most appropriate policy response. We make use of data from a variety of studies, including the National Pupil Database (NPD), the Millennium Cohort Study (MCS), the Avon Longitudinal Study of Parents and Children (ALSPAC), the Longitudinal Study of Young People in England (LSYPE), the Labour Force Survey (LFS) and Understanding Society. For most of our analysis, we use simple regression models to identify mean differences in outcomes between individuals born at different times of the year.