As part of the Expanding Children’s Early Learning Network (ExCEL) project, MDRC is partner­ing with with the Boston Public Schools (BPS) Department of Early Childhood, the University of Michigan, and the Harvard Graduate School of Education to understand how BPS’s reforms to align instruction across the early grades supported teaching and learning. The purpose of this brief is to assess the feasibility of using naturally occurring lotteries to evaluate the effects of BPS’s Focus on Early Learning approach on students over time; results from a full impact study estimating effects on student outcomes will be released in 2023. The brief begins by presenting background information on the approach, the motivation for the study, and the project’s core research aims. (author abstract)