The Understanding Children's Transitions from Head Start to Kindergarten (HS2K) Project was a multi-year project funded by the United States Department of Health and Human Services, Administration for Children and Families, Office of Planning, Research and Evaluation. The purpose of this project was to better understand how to improve children's transitions from Head Start programs to elementary schools. The transition to kindergarten occurs within and between two distinct systems (early care and education [ECE] and K-12 education) that each work under their own governance structures, philosophies, and accountability metrics. Specifically, this project aimed to explore the definition of "successful transitions" from a multi-level and systemic perspective. Within the context of this project, the focus is on one type of ECE program--Head Start. Head Start is embedded within a broader "ECE system" that includes many other types of programs, including state-funded pre-k, child care, home-based care, friend and family care, and privately-funded centers. This report details findings from one component of the HS2K Project -- a comparative multi-case study of five Head Start and Local Education Agency (LEA) partnerships, including their families, Head Start teachers and leaders, kindergarten teachers, elementary school leaders, LEA leaders, and community partners. The case-specific descriptions should be read as in-depth illustrations of the inner workings of kindergarten transition processes as they existed and were implemented in context at the time of data collection.