A 4-yr old who randomly won a seat in Boston preschool:
-likelihood of graduating HS (6 p.p.)
-likelihood of attending college (5.4 p.p.)
-suspensions and likelihood of juvenile incarceration
-likelihood of SAT above bottom quartile.
https://www.nber.org/papers/w28756 

While we've known since the Perry School experiments in the 1960's that quality preschool can improve long-term outcomes, whether the benefits can be gained at scale in a non-lab setting has been an open question.

Beyond that, achievement gains from early interventions often fade out, which sparked debate regarding whether the benefits were enough to offset the costs of universal public preschool. Thankfully, policymakers in many states decided to pilot universal pre-K programs.

Boston offers free, universal pre-k for 3 and 4 year olds in programs operated at public schools and taught by certified teachers. However, there are only seats for about 50% of eligible kids, so Boston runs an admissions lottery as a tiebreaker for oversubscribed seats.

The authors here examined data from 4 yr. old lottery winners and compared them to applicants who, due to random chance, did not get a pre-k seat. They then collected data on the long-run achievement, disciplinary, and college attainment outcomes for all students.

In addition to the effects summarized above, they found stronger effects for boys, which is a promising means to close the gender-based educational attainment gap, and null effects on achievement.

The study ultimately fills two neat gaps: 1) pre-k benefits seem to operate through behavioral changes and non-cognitive skills important for success in school and identification with school rather than through enhanced learning. 2) The benefits can be realized at scale.

As the Biden administration pushes for federal funding for universal preschool, keep this study in mind. The benefits suggested here are immense AND the study only considers the direct benefits for children, not the indirect labor market benefits to parents.