Alongside the birth of a sibling, the transition to school is the first major event in many children's Lives. This period is, for most children, exciting and enjoyable but it also brings social, practical and academic demands that some find challenging. Longitudinal studies confirm the importance of individual differences in early school success, but explanations remain elusive. Challenges include the lack of consensus about how 'school readiness' should be defined, the dearth of simple measurement tools, and difficulties in making causal inferences about family influences on children's development. Nonetheless, recent years have seen progress in research, leading to interventions that could narrow the achievement gap between children from affluent and disadvantaged families.