A recently published book has some interesting findings on the causal chain of events by which high-quality preschool education has long-run effects on adult outcomes.

The book is “Childhood Programs and Practices in the First Decade of Life”. I recommend the entire book for your reading. The book includes summaries of research findings on many preschool programs, other early childhood programs, and early elementary programs, including the Nurse Family Partnership, Head Start, Perry Preschool, the Abecedarian program, the Child-Parent Center program, state-funded preschool programs in New Jersey, Michigan, and Oklahoma, and the Tennessee class-size reduction study.

However, in this post, I will focus on the book’s last chapter. This last chapter is written by Arthur Reynolds, Michelle Englund, Suh-Ruu Ou, Lawrence Schweinhart, and Frances Campbell. It tries to synthesize results from three of the best studies of long-run effects of preschool: the Perry Preschool program, the Child-Parent Center program, and the Abecedarian program.

The goal of this synthesis is to explore the causal mechanisms by which these preschool programs lead to higher educational attainment at age 21. What is the “chain of events” that leads from high-quality preschool to more educational attainment at age 21?

Somewhat surprisingly, more educational attainment at age 21 is NOT primarily due to higher academic achievement in high school as measured by higher literacy test scores in high school, or at least is not due to such test scores once one controls for other causal influences.  Instead, greater educational attainment at age 21 is more consistently predicted by whether the student has become involved in juvenile crime, and whether the student has been assigned to special education or retained in grade by age 14. Of course, becoming involved with crime, being assigned to special education, or being retained in grade, may be associated with lower high school test scores. But once one controls for crime/special education/grade retention, the high school test scores are not as important in predicting educational attainment by age 21.

Going back in the causal chain, whether a student is eventually retained in grade or assigned to special education is often predicted by a student’s academic motivation and social adjustment in early elementary school.  These are “soft skills” in early elementary school. These soft skills can be shown to be predicted in part by the student’s gain in “hard skills” – academic test scores – at kindergarten entrance, due to high-quality preschool or other interventions. Presumably the student’s gain in soft skills by kindergarten entrance also matters, but this is not included in this chapter’s analysis.

The implication is that soft skills, and how they alter a student’s relationship to school and the community, play a key role in determining educational attainment at age 21.

Another chapter in the book, by Flavio Cunha and Nobel prize-winning economist James Heckman, suggests that “soft skills” may be even more important in determining adult earnings than in determining educational attainment. Early investments in soft skills, and early investments in hard skills, are roughly equally responsible for predicting adult earnings in the mid-20s. Early investment in soft skills not only leads to further development of soft skills, but also helps improve later hard skills.

Both soft skills and hard skills are intertwined in yielding the long-run effects of high-quality preschool in boosting adult earnings of former participants. A high-quality preschool program should balance the goals of boosting both hard skills and soft skills.