This paper concentrates on children's play during school breaktimes. Though neglected by researchers, it is one of the few occasions when children can play and interact in a relatively safe environment, free of adult control. The paper reports on a recent programme of research at the University of London Institute of Education. There are signs that the prevalence of a negative view about breaktime in schools is leading to more deliberate management and supervision of breaktimes, and a reduction in duration. Breaktime can be a time when aggression, teasing, and bullying take place, but this paper also reviews positive aspects of peer relations and games at breaktime, including opportunities for friendship development, social competence, and peer culture. An important challenge facing schools is achieving a balance between control over pupil behaviour, while facilitating pupil independence and social development.