From a recent NPR article:
“Is preschool worth it? Policymakers, parents, researchers and us, at NPR Ed, have spent a lot of time thinking about this question.
We know that most pre-kindergarten programs do a good job of improving ‘ specific skills like phonics and counting, as well as broader social and emotional behaviors, by the time students enter kindergarten. Just this week, a study looking at more than 20,000 students in a state-funded preschool program in Virginia found that kids made large improvements in their alphabet recognition skills.
So the next big question to follow is, of course, Do these benefits last?
New research out of North Carolina says yes, they do. The study found that early childhood programs in that state resulted in higher test scores, a lower chance of being held back in a grade, and a fewer number of children with special education placements. Those gains lasted up through the fifth grade….
The big difference between the long-term findings in North Carolina and Tulsa and the fade out in Tennessee, researchers say, is the quality of the preschool program.
Having a high-quality program is key, says Dodge. ‘The long-term impact,’ he says, ‘depends entirely on quality and how well elementary schools build on the foundations set in pre-K.'”