Abstract. Figures are showing that ethno-cultural issues are increasingly related to most school bullying incidents happening lately. While many theoretical arguments and empirical investigations scrutinize the effects of foreign migration on hostile behaviours enacted by the adult population, there is insufficient evidence on the effects of immigration on youth. This paper provides evidence by exploiting the shock from migration which occurred in the UK after the 2004 European Union Enlargement to estimate the magnitude and the directionality of the effect exerted by the resulting inflow of migrants on school bullying. Multilevel Logit, Generalized Estimating Equations and Control Function with Two-Stage Residual Inclusion are used on a novel dataset containing spatially fine-grained observations on school bullying across the UK. Findings highlight a relevant effect of the shock from migration in triggering bullying, which is robust to the accounting for potential endogeneity with respect to immigrants’ location choice. The role of existing language barriers as channel for the effect of the migration shock is also scrutinized, to find that they increase its effect.