https://www.fcd-us.org/do-the-short-term-effects-of-a-strong-preschool-program-persist/
Beginning in 2001, researchers at the Georgetown University Center for Research on Children in the United States (CROCUS) have evaluated the effectiveness of the Tulsa Public Schools PreK program.
Do the Short-Term Effects of a Strong Preschool Program Persist?, is a Policy Brief on the longer term effects of the Tulsa PreK program.