While some states use common early childhood assessments during preschool, most states begin assessing children’s skills and knowledge with a kindergarten entry assessment (KEA). KEAs, administered in the early weeks of kindergarten, provide a snapshot of individual children’s development. Some of these KEAs are part of assessment systems that begin before kindergarten and/or continue throughout the kindergarten year or into the primary grades. As of 2021, 38 states have a KEA—more than a fivefold increase in 10 years, which was spurred by federal policy that required states receiving Race to the Top–Early Learning Challenge grant funds to implement statewide KEAs. As KEAs have become more common, they have been subject to several kinds of controversy. Assessments that are highly scripted, inauthentic, or too long can be inappropriate for young children and unfeasible for teachers. Assessments that are narrowly focused on discrete skills and exclude essential developmental domains can, if they are used in a high-stakes fashion, limit early childhood curriculum and foster inappropriate teaching strategies. Bias in assessment design or in implementation practices can lead to deficit perspectives of certain children, such as those from diverse cultural or linguistic backgrounds or those with special needs. Given the widespread and growing use of KEAs, this report aims to inform policymakers about the features of KEAs and other early childhood assessments, the implications of using different kinds of assessments, and the possibilities for supporting high-quality early learning through well-chosen and well-implemented assessments. We sought to answer several questions: What types of assessments are currently used at kindergarten entry? What might policymakers look for in a high-quality assessment? What training and support are states providing to support the effective use of KEAs for instruction? How are states supporting continuous improvement of their KEA systems, and what cautions can be gleaned from their experiences? (author abstract)