Controversial findings on the role of school ethnic diversity on ethnic bullying and victimization suggest the relevance of different categorizations of ethnicity in understanding this association. The present study aims to use an operationalization of both social/legal (i.e., citizenship status) and perceptual (i.e., others' perception of diversity) aspects to analyse the impact of ethnic diversity on ethnic bullying and victimization, considering both individual and classroom-level associations. Participants were 960 students (52% girls; M = 15.19; SD = 0.60) from 58 first-year high school classrooms. Multilevel analyses showed that the lack of Italian citizenship appeared to be a risk factor for ethnic victimization on both individual and classroom levels, over and above the differences in students' perceptions. No effects were found for ethnic bullying perpetration.