Some early childhood experts assert that the effects of preschool may diminish if curricula and instructional strategies from preschool through grade 3 are not well aligned. A second explanation for why initial benefits of preschool may not persist is that children who make early gains in preschool may not have the opportunity to maintain their growth rate or learning trajectory because early elementary instruction may focus on students who are less prepared and have low-level skills. This "Results in Brief" highlights findings from a literature review aimed to better understand the research behind these two theories and focused on preschool and K-3 alignment and differentiated instruction in kindergarten and first grade. The review of differentiated instruction excluded studies that focused exclusively on low-achieving students because of the priority on differentiated instruction as a way to help sustain the gains children make in preschool. This brief describes the study questions, design, and findings from the full report. [For the full report, see ED613465.]