Background Owing to the limited effectiveness of traditional health education curricula in schools, there is increasing interest in interventions aiming to promote young people's health by modifying the school environment. Existing systematic reviews cannot determine whether environmental intervention is effective because they examine interventions combining environmental modifications and traditional health education. This gap is significant because school-environment interventions are complex to implement and may be sidelined in underfunded and attainment-focused school systems without evidence to support such an approach. This systematic review examined the effectiveness of school-environment interventions without health-education components on student health and inequalities. Methods This was a systematic review of experimental/quasi-experimental studies of school-environment interventions. Sixteen databases were searched, eliciting 62 329 references which were screened, with included studies quality assessed, data extracted and narratively synthesised. Results Sixteen reports of 10 studies were included, all from the USA and the UK. Five evaluations of interventions aiming to develop a stronger sense of community and/or improve relationships between staff and students suggested potential benefits particularly regarding violence and aggression. Two trials of interventions enabling students to advocate for changes in school catering and physical activity reported benefits for physical activity but not diet. Three evaluations of improvements to school playgrounds offered weak evidence of effects on physical activity. Conclusions School environment interventions show the potential to improve young people's health particularly regarding violence, aggression and physical activity. Further trials are required to provide a stronger and more generalisable evidence base.