This review explored the research regarding the effects of school-based wellbeing interventions on student academic achievement (N = 320,505) and the wellbeing-related outcomes (N = 411,535) of social-emotional adjustment, behavioural adjustment, cognitive adjustment, and internalising symptoms. There were 75 studies that qualified and were included in the final analyses which involved 432 extracted outcomes from students 5 to 18 years of age. This review found that school-based wellbeing programs had a small positive effect on academic achievement, equivalent to two months of additional impact (g = 0.17). Wellbeing programs had small to moderate effects on wellbeing-related measures: social-emotional adjustment (g = 0.14), behavioural adjustment (g = 0.15) , cognitive adjustment (g = 0.18), and a moderate impact on internalising symptoms (g = 0.20) compared to 'business as usual', consistent with previous reviews.