Abstract
Schools are important settings for intervention to improve mental health. Much school mental health research has focused on schools as an avenue to reach large numbers of young people with new interventions, added on top of what schools currently do. However, research is increasingly focused on changing the school system itself to improve mental health, with a growing emphasis on improving school climate. This article begins by exploring wider debates on the benefits and harms of school-based interventions, before focusing on school climate as a target for intervention. It reviews evidence from intervention studies and systematic reviews to understand effectiveness, how interventions reduce or amplify inequalities, and real-world impacts. School climate research has grown rapidly since the turn of the century. It remains difficult to define. Definitions vary in whether they include focus on physical environments and educational instruction. However, they converge on focus on positive relationships among a school community and safety. Several large trials of interventions to improve mental health, by improving school climate, have been conducted in a range of international contexts. While many have not been effective, recent trials provide evidence that interventions can improve school climate and mental health, as well as a range of risk behaviours. Few studies examine effects on inequalities in mental health, with tentative evidence that school climate interventions have been more effective for some groups than others (e.g., bigger effects for boys than for girls). Evidence on scalability and sustainability indicates that typically small effects from trials may not fully translate into real-world change. There is growing evidence that improving school climate interventions can improve child and adolescent mental health. More research is needed on how such interventions can contribute to reducing inequalities. Further work is needed to understand how effects translate into real-world public health impact.