Depression in children and adolescents is considerably undertreated, and the school may be a good setting for identifying and treating depression. We conducted a meta-analysis of studies in which students were screened for depression, and those with depressive symptoms were treated with a psychological intervention. Only randomised controlled trials were included. Eight studies met the inclusion criteria. Five studies focused on younger children (7-14 years) and three studies were aimed at adolescents (12-19 years). In total 5803 students were screened, of whom 7.2% were included in the intervention studies (95% CI: 7.1-7.3). The 'numbers-needed-to-screen' was 31 (95% CI: 27-32), which means that 31 students had to be screened in order to generate one successfully treated case of depression. The effects of the psychological treatments at post-test were compared to control conditions in the 8 studies comprising 12 contrast groups, with a total of 413 students. The mean effect size was 0.55 (95% CI: 0.35-0.76). There were not enough studies to examine whether specific psychotherapies were superior to other psychotherapies. Although the number of studies is small and their quality is limited, screening and early intervention at schools may be an effective strategy to reduce the burden of disease from depression in children and adolescents. More research on the (negative) effects of these interventions is needed.