The growing movement to strengthen PreK-3rd education as an essential foundation for student success, along with the rapid expansion in public funding for PreK, has created an urgent need to measure children's educational progress, in a continuous fashion, from the beginning of PreK through Grade Three. Currently, some state governments are building longitudinal data systems that aim to: (1) Provide information on teachers and programs; (2) Identify students who would benefit from intervention and other services; (3) Evaluate programs, schools, principals, and teachers; and (4) Inform local and state policy decisions. These efforts have been implemented, in large part, with federal investments from the U.S. Department of Education's Institute of Education Sciences and the American Recovery and Reinvestment Act of 2009 (Data Quality Campaign, 2011 (a, b, & c); Jennifer Cohen, 2010). Most data system development efforts, however, focus on K-12, with little or no attention paid to PreK education. It is essential that PreK data be included in state longitudinal data systems, because this is the only way in which it will be possible to analyze how the PreK experiences children have (or have not had) are related to later achievement in K-12 and beyond. Building on the work of the Data Quality Campaign (2011b), this brief recommends that the federal government convene a national advisory group, made up of policymakers, educators, researchers, and technical experts to develop guidelines that will help states create longitudinal data systems for PreK-3rd Grade. The group should help states in three key areas: (1) Fully integrating PreK data from both public and private programs into state longitudinal data systems; (2) Designing and implementing three distinct "electronic gateways" or "portals" to make appropriate levels and types of information available to a variety of stakeholders; and (3) Revising laws and regulations to maintain student confidentiality while ensuring easy and timely access to information. (Contains 2 footnotes and 50 online resources.)