This study examined the impact of Head Start duration on children's language and mathematics skills based on the nationally representative sample of the Head Start, Family and Children Experiences Survey (FACES, 2009). Analysis of the FACES (2009) revealed that children who attended Head Start for two years displayed substantial advantages both in language and math skills compared to one-year attendees by the time they left Head Start. These advantages were sustained until the end of kindergarten with a slight reduction of the effect sizes. This study adds to the growing body of evidence that a longer exposure from an earlier age to a public preschool program plays a significant role in improving the academic skills of children from economically disadvantaged families. (author abstract)