Children moving from early education programs into elementary schools face a critical transition, making it important for both systems to coordinate to better serve our youngest children. Yet, there is limited research on coordination around the transition to school. The objectives of this dissertation were to: 1) describe the coordination efforts used by Head Start programs to smooth children's transitions to kindergarten, 2) examine the association between coordination and children's outcomes in kindergarten, 3) test whether there is an interaction between Head Start coordination efforts and elementary school-based transition practices, 4) test interactions between coordination and child/family characteristics, and 5) understand the benefits and challenges to coordinating across systems. This study included two phases. Phase I examined coordination efforts between Head Start programs and elementary schools in a nationally representative sample of Head Start children (N=2,019). Findings suggest that Head Start programs are engaging in a variety of activities to coordinate with elementary schools. Results of regression analyses found that coordination was positively related to children's language and mathematics skills in kindergarten for children enrolled in elementary schools engaging in limited activities to support the transition to school. Phase II involved interviews with sixteen Head Start directors. Results showed multiple ways they coordinate with elementary schools to share information about individual children and general program practices, as well as the ways they serve as a bridge between families and elementary schools. Findings suggest that coordination may benefit children through improved practices by Head Start and elementary schools, as well as increases in parental readiness and involvement. Overall this study shows that Head Start programs are engaging in multiple activities to coordinate with elementary schools. Although direct relationships between coordination practices and child outcomes were limited, interviews with Head Start directors pointed to indirect pathways by which coordination efforts may benefit children. These findings suggest the importance of coordination practices, and stress the need for additional research to explore these pathways. (author abstract)