The Massachusetts Preschool Expansion Grant (PEG) model supported and expanded high-quality preschool in high-needs communities. PEG required shared governance between local school districts and Massachusetts Department of Early Education and Care-licensed community-based programs. The 48 PEG classrooms provided free prekindergarten for four-year-olds from low-income families who were eligible for kindergarten the following year and who, with some exceptions, had not yet attended a formal child care program. As part of the PEG evaluation, this impact study found: (1) On all three measures of early academic performance, PEG had a positive and statistically significant impact on children's achievement, with the strongest impacts on the most vulnerable children; and (2) Exploratory analyses indicated that the impact of PEG was stronger for children in homes where English was not the primary language and for children who had not had prior child care exposure.