Research shows that high-quality pre-K can have lasting impacts on children’s learning and development, with the largest effects clustered among children of color, multilingual learners, and children from low-income backgrounds. Yet policymakers, administrators, and teachers often wrestle with the complexities of providing these programs on a large scale and in rapidly evolving contexts. A key challenge is the lack of reliable, unbiased data about children’s skills, knowledge, behaviors, and classroom experiences—information that could guide teacher practice and inform investments in early learning systems. MDRC is leading an initiative, Measures for Early Success, aimed at shifting the assessment landscape across the early learning field. This brief presents some starting points the team will examine with states, districts, other pre-K providers, and researchers.