Migrant adolescents often experience elevated levels of mental health difficulties, but also notable resilience. As a primary developmental context, school provides a crucial setting for promoting adaptation and wellbeing, with teachers serving a central role. Psychosocial, multi-tiered school interventions demonstrate potential for providing both universal and targeted student support. This thesis examined wellbeing profiles and their determinants among immigrant and refugee adolescents, as well as the association of teachers’ multicultural attitudes on their self-efficacy and wellbeing. It also presents the protocol and effectiveness study of two psychosocial school interventions aimed at enhancing migrant adolescents’ wellbeing. The findings are discussed through ecological, acculturation, and resilience frameworks.

The data of this thesis derives from the RefugeesWellSchool project, a European collaboration across six countries examining psychosocial school interventions for migrant student wellbeing. Students and teachers completed self-report surveys at baseline, post-intervention, and follow-up. This thesis employed cross-sectional data from 1607 migrant students and 433 teachers across all countries, and longitudinal Finnish data from 1974 native and migrant students.
Four wellbeing profiles emerged among migrant students, differing especially in PTSD symptom patterns. Refugee background, older age, discrimination, daily stress, and low family support were linked to profiles with poorer mental health. Among teachers, positive multicultural attitudes associated with greater work dedication, but not with work exhaustion. Self-efficacy mediated the association between multicultural attitudes and work-related wellbeing. Finally, the psychosocial interventions were generally not effective in increasing wellbeing; their benefits varied by students’ age, gender, and exposure to stress and discrimination.

This thesis deepens understanding of migrant adolescents’ wellbeing, highlighting how individual and contextual factors shape both wellbeing and intervention outcomes. It also emphasizes teachers’ multicultural attitudes as important to both their wellbeing and efficacy beliefs. Overall, this doctoral thesis advocates for multidimensional, culturally informed collaboration across education, mental health, and social systems to better support migrant youth.