This study examines how the age at which children enter Head Start affects their academic and behavioral outcomes. Data from the National Longitudinal Survey of Youth are incorporated to analyze the progress of 1,553 Head Start children. The research examines outcomes through assessments conducted at ages 5-6 and at ages 11-12. The results suggest that the measured outcomes vary with complicated interactions among age at Head Start entry, maternal education levels, and maternal verbal test scores. In many cases, early age of entry is estimated to improve outcomes for children whose mothers have low education and test scores. (author abstract)