States are working to build comprehensive early childhood assessment systems to answer key questions about young children’s learning and development and the effectiveness of early childhood programs. Research and best practice will help states as they make decisions and provide leadership in developing, adopting and providing guidance on assessment of children, programs, and educators; providing professional development on how to administer and use the results of assessments; and supporting timely, useful reporting of assessment data to early childhood programs, teachers, families, school districts and state policymakers.