In many parts of the world, children are legally obliged to attend school at a particular age. The age at which compulsory education begins can range between three and seven years. Being ready for school could have life-long benefits. School readiness covers elements of a child’s development that promote learning such as positive behaviour, emotional well-being, social skills and intelligence. Interventions can foster play and sharing, listening skills and emotional regulation which all help contribute to a positive learning environment. We wanted to find out if attending a centre-based early education programme for school readiness was better than not attending any programme or receiving a standard pre-school programme. This Campbell systematic review examines the effects of school and centre-based education programmes on school readiness, compared to no treatment or treatment as usual. The review summarizes evidence from 32 studies. Centre-based interventions may have little to no effect on school readiness but we are very uncertain about the results. Future studies should consider how best to measure school readiness, and over a longer timeframe.