There is an ever-increasing concern about the apparently increasing amount of violence and aggression in our schools. This increase in violent behaviour has also been accompanied by a decrease in the average age for violent offenders. In the school setting, aggression and victimisation is increasingly being recognised as psychologically, physically, and academically damaging. This aggression and victimisation can readily be observed in acts of peer bullying. Bullying may take the form of a range of anti-social behaviours such as name calling, extortion, physical violence, nasty rumours, exclusion from the group, damage to property, and threats; and may occur in 10% of students in Australian schools at least once a week. For bullies, aggression may persist into adulthood in the form of criminality, marital violence, child abuse and sexual harassment. For victims, repeated bullying can cause psychological distress and many related difficulties, and even suicide. However, despite the pervasiveness of the issue and the handful of intervention programs that have been designed to prevent bullying, there have been few attempts to explain the possible reasons of why bullying occurs or is maintained within the school setting. This theoretical paper examines the contribution which self-concept theory may bring to this vexing issue, how self-concept may have differential influences on bullies and victims, and what implications these influences have on educational and health practices. The paper also describes a collaborative project which is currently looking into this question.