Understanding predictors of offending is essential for developing effective crime prevention. Educational attainment is a readily available metric for pupils in many countries, with performance on standardised tests often systematically collected throughout school. If changing attainment is associated with offending risk, it could present a signal to check in with pupils and offer appropriate support. We analysed an existing linkage between the National Pupil Database and the Police National Computer in England. In a cohort of 4.3 million pupils born between the academic years 1990/91 and 1996/97, we modelled trajectories of standardised attainment on statutory tests at ages 7, 11 and 16 years. We then investigated the association between these attainment trajectories and subsequent first offence convictions or cautions during young adulthood. Among pupils showing relative declines in attainment over their school career, 1 in 3 were convicted or cautioned for a first offence before the end of school, and 1 in 10 were convicted or cautioned for a first offence during young adulthood. Additionally, among pupils who performed at below average levels towards the beginning of school, their odds of offending during young adulthood were 53