Abstract
Schools are increasingly culturally diverse. Yet, it is unclear whether a positive school diversity climate influences students' academic achievement and social well-being, and the role of school belonging in explaining this effect. A total of 1156 adolescents (Mage = 15.69, 51.65 % females and 48.35 % males) residents in the Emilia-Romagna region, Italy, participated in a longitudinal study with four assessments across one year. Most participants (78.96 %) belonged to the majority group (i.e., both they and their parents were born in Italy), while 21.04 % had a migrant background (i.e., themselves or at least one of their parents was born outside Italy). Results highlighted meaningful associations between school diversity climate and adolescents' academic achievement and social well-being. Concurrently, both perceived equal treatment and support for contact and cooperation were associated with adolescents' higher academic achievement and social well-being. Longitudinally, perceived equal treatment by teachers led to a higher sense of school belonging, contributing to increased social well-being. Students' migrant background moderated the impact of school diversity climate on youth's social well-being. Overall, findings highlight how inclusive schools can generate more inclusive societies.