"PK-3" has become a rallying cry among many developmental scientists and educators. A central component of this movement is alignment between preschool and the early elementary grades. Many districts have made policy changes designed to promote continuity in children's educational experiences as they progress from preschool through third grade--to provide children with a seamless education that will sustain the gains made in preschool and lead to better developmental and learning outcomes overall. This report proposes a conceptualization of productive continuity in academic instruction, as well as in the social climate and classroom management practices that might affect children's social-emotional development. It also considers ways in which schools might seek to achieve continuity in parents' and children's experiences. Finally, the report proposes specific state and district policies and school practices that are likely to promote continuous and meaningful learning experiences. (author abstract)