High-quality early childhood programs aim to foster children's learning through developmentally appropriate practices and environments. Early childhood assessments, when well designed and well implemented, can support developmentally appropriate early learning experiences by providing information to guide instruction and support whole child development. 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. This report has examined prior research on assessing young children, scanned practices across states and districts, and highlighted promising examples to illuminate how KEAs can support equitable learning. It provides insights into how to choose high-quality assessments, the implications of different assessment choices, and how to effectively use KEAs as part of strong statewide early learning assessment systems. [For the research brief, see ED614432.]