The diverse benefits of nature are increasingly well-known, but access to nature and its associated benefits are inequitable. In parallel, because school attendance is compulsory, schools are ubiquitous in every community. However, only a small fraction extend classroom settings into outdoor spaces developed as educational resources richly endowed with nature. By greening schoolyards, every community in the United States would provide safe, accessible, natural areas, greatly expanding available educational space and resources benefiting the entire school community. Greening schoolyards offers a promising strategy to ensure all children and communities have access to the health, wellness, learning, and myriad other benefits contact with nature provides. This paper makes the case for green schoolyards as a tool for providing access to nature for all children and sets a research agenda to support that goal.