Forty-four Head Start classrooms were randomly assigned to enriched intervention (Head Start REDI—Research-based, Developmentally Informed) or “usual practice” conditions. The intervention involved brief lessons, “hands-on” extension activities, and specific teaching strategies linked empirically with the promotion of: (a) social-emotional competencies and (b) language development and emergent literacy skills. Take-home materials were provided to parents to enhance skill development at home. Multimethod assessments of three hundred and fifty-six 4-year-old children tracked their progress over the course of the 1-year program. Results revealed significant differences favoring children in the enriched intervention classrooms on measures of vocabulary, emergent literacy, emotional understanding, social problem solving, social behavior, and learning engagement. Implications are discussed for developmental models of school readiness and for early educational programs and policies.