In this paper, the 21st Century School Fund and CC&S add to the growing conversation about and demand for joint use as a way to provide services to children and families in convenient locations, improve opportunities for physical activity by increasing use of school recreational and outdoor spaces, leverage capital investments, and more, we provide a conceptual frame for the joint use of PK-12 public schools. This paper establishes definitions for joint use and frames the basic challenges and opportunities for facilitating better conversations and planning for these type of collaborations.