An interesting policy to evaluate from a health perspective would be universal pre-k. This program ensures that all children have the opportunity to go to a pre-k program before entering kindergarten. There are clear (and documented) educational benefits for the children enrolled, but educational access may lead to additional benefits to their health and the health of their families. Being enrolled in pre-k provides children and their families with access to social programs they may not have been aware of if they are not accessing those systems otherwise. Early intervention programs for those with learning difficulties or developmental delays would be accessible through these pre-k programs and lead to improved performance in elementary school and beyond. Health content is provided in schools so it would be understandable if hand washing or dental health habits improved due to exposure to the topics in school by the children and parents were made aware of it. It would also be interesting to see if the expenditure that is diverted from day-care costs to other costs would be put toward preventing health problems or food insecurity (much like it is hypothesized the EITC does).
There are a number of nature experiments to test the hypothesis that access to universal pre-k improves the health of children because a number of states (~40) have these programs. The National Institute of Early Education Research has done a lot of work in the area of whether these programs impact later learning and how they compare with other programs like subsidies for child care. It would be interesting to understand the connection between universal pre-k and the health outcomes we know are related to education – like smoking and access to healthcare. Racial disparities in these groups are key to understand because of the differences seen in those outcomes by race and SES and the use of a universal pre-k program by race and SES.
I did not find a study looking at these issues during a quick search. But an ideal study design to highlight the effect of universal pre-k on health is use of data from a cohort study already in progress. Students who were enrolled in pre-k could be compared to those who were not enrolled and followed to adulthood to compare health outcomes. It would be interesting to look at lifestyle factors because of the links to heart disease and diabetes, but also access to care, the health of others in the family, and health beliefs. In the case of universal pre-k, there is so much time passing between the intervention and the outcomes of health later in life. This presents a challenge in drawing inferences about its effect and opens any research up to scrutiny because of potential confounders which occur during the child's life.