School suspensions are commonly used in schools to address challenging student behaviours, often on the understanding that suspensions send a clear message to the school community about what is acceptable behaviour. However, there is a growing body of evidence that school suspensions have a range of unintended negative consequences including academic failure, school drop out, alienation, substance use, and crime and delinquency. This research has examined the impact of school suspensions on subsequent antisocial and violent behaviour, above and beyond many established influences on student behaviour. It shows that school suspensions increase the likelihood of antisocial and violent behaviour 12 months later. The implications of these findings for schools, together with alternatives to the use of suspensions, are discussed. (Contains 2 tables and 1 figure.)