Over the past decade, states have dramatically expanded prekindergarten services (Pre-K), given the evidence that high-quality early childhood education can put children on a path to success in school and later life. To support the expansion, most of those states have adopted a mixed delivery system, developing the new educational opportunities in both public schools and early childhood programs in the community, a strategy that leverages the existing capacity, expertise, and public investments that support early learning and healthy development. Such a system has the potential to more rapidly expand the availability of high quality early education and also offers families a choice of preschool settings. Increasingly, educators and policymakers are looking at strategies to align learning experiences, enrich services and family supports, and build a unified early education system so that all children benefit equally regardless of setting. Great progress has been made on this front, but developing and implementing an integrated, coordinated state Pre-K system is challenging. The two worlds of public education and early childhood development are still far from aligned, operating with complex governance and funding sources, in addition to different strategies and approaches to practice. This paper provides a summary of specific challenges that New York communities have encountered as they developed and implemented a mixed system for providing prekindergarten services. By anticipating these challenges, school districts and community-based early education programs can develop strategies to support effective partnerships, successful program implementation, and improved school readiness for young children. A combined list of references and other sources is provided.