This ambitious monograph tackles several important questions related to children's preschool experiences that have relevance for program and policy initiatives at the state and federal levels. The authors' approach is rigorous: they conduct parallel analyses across eight large and diverse studies of preschool children in center care and use meta-analysis to summarize patterns across studies. The study finds nonlinear associations between preschool quality and gains in language and literacy skills, with larger associations in higher versus lower quality classrooms. Results also show that domain-specific measures of preschool quality were more strongly related to children's development than global quality measures. The "dosage" of preschool was likewise important: more years in Head Start predicted larger vocabulary and literacy gains, whereas more time spent on instruction predicted greater literacy and math skills growth. In this commentary, we situate these findings in the broader literature addressing links between preschool experiences and children's development and discuss key takeaways for research, practice, and policy. (author abstract)