the hsis study concludes, "head start has benefits for both 3-year-olds and 4-year-olds in the cognitive, health, and parenting domains, and for 3-year-olds in the social-emotional domain. however, the benefits of access to head start at age four are largely absent by 1st grade for the program population as a whole. for 3-year-olds, there are few sustained benefits, although access to the program may lead to improved parent-child relationships through 1st grade, a potentially important finding for children's longer-term development."