DISCUSSION
The present meta-analysis synthesized the empirical literature on controlled evaluations of elementary school-based mental health services delivered by school personnel, computing overall pooled effects across studies, and determining factors associated with variations in the effects. Services delivered by school-based personnel collectively demonstrated a small-tomedium effect on child mental health problems, with particularly large effects associated with targeted interventions and selective prevention, services that included contingency management, services that were integrated into academic instruction, services that were implemented multiple times per week or daily, and services that targeted externalizing problems. These findings build on prior reviews27,28,73,74 and provide quantitative support for prioritizing the integration of mental health care within school settings.73,75 Against a concerning backdrop of serious problems in the accessibility of evidence-based treatments for youth,13,14,76 the present meta-analysis provides evidence of the important role that school-based personnel who are naturally in children’s lives can play in implementing mental health services. Notably, universal prevention showed somewhat weaker effects relative to more targeted services. This is consistent with previous qualitative reviews and meta-analyses27,77 and may reflect floor effects commonly found in prevention science when intervening with an entire population rather than with a selected subset of individuals with more documented need.78 Importantly, despite the relatively weaker effects observed for universal prevention, small effects can still yield large impacts.79 Indeed, universal prevention can play a critical role in reaching a larger population of children, can reduce stigma by including all children, and can increase school and parent involvement.27,80 Although the present findings document particularly encouraging outcomes associated with selective prevention and targeted interventions and underscore the need to more broadly promote their uptake in schools, universal preventions must nonetheless remain a critical component of school-based mental health care.