Exclusion from school and risk of serious violence: a target trial emulation study

Expulsion or exclusion from school is a common event in the lives of people who have experience of the criminal justice system. Exclusion underpins the ‘school-to-prison pipeline’ and is, accordingly, one of the most contentious policies used in education systems. Critics of exclusion powers claim that it is a direct cause of later offending behaviour, among other adverse outcomes, while supporters of this power argue that it is necessary for maintaining school discipline and safety. Evidence for or against a causal effect of exclusion on offending is inhibited by random allocation of exclusion not being available on ethical grounds and the generally low internal validity of studies in this area. To advance understanding of the causal connection between school exclusion and offending – specifically, serious violent offending – this study leverages a recent national linkage of educational and criminal justice records in England to emulate a randomised controlled trial using a target trial framework. Across more than 20,000 matched pairs of excluded and not excluded children, within twelve months of target trial entry, the hazard ratio for serious violence was 2.04 (95% CI: 1.83, 2.28) and for homicide/near-miss homicide was 2.36 (95% CI: 1.07, 5.20). We discuss the implications of these findings for theory and policy in education and criminal justice as well as discussing the extent to which the observed relationships can be considered causal.