Recent decades have seen a rise in mental health problems among children and adolescents. Despite a proliferation of studies describing effective school-based mental health programs, reviews of current research in this field suggest a strong lack of consensus concerning the definition of school mental health and its constructs. In the present paper, we set out to fill this gap via a two-step process: first, we offer a critical overview of recent research around the concept of school mental health; second, we propose a comprehensive theoretical framework for researchers, practitioners, and policy-makers involved in mental health promotion and school prevention programs. The proposed framework comprises three key domains: the first two, cover the promotion of social and emotional learning and resilience, while the third concerns the prevention of behavioural problems.