FRIDAY, May 3, 2024 (HealthDay News) -- Pre-kindergarten programs have long been considered an early ticket to future success for children.

But the evidence is much more mixed than one might think regarding the longer-term effectiveness of preschool programs, a new evidence review in Science says.

More recent published evaluations of well-established preschool programs have reported a mix of positive, negative and no difference for children’s later academic achievement, researchers say.

“Preschool programs have long been hailed as effective interventions, yet our study reveals a more nuanced reality,” senior researcher Margaret Burchinal , a research professor with the University of Virginia’s Center for Advanced Study of Teaching and Learning, said in a news release.

The idea that these programs can help children succeed in school – particularly kids hampered by income- and race-based achievement gaps – initially came from a pair of prominent clinical trials conducted more than 50 years ago, researchers said.

However, recent studies have shown that’s not always the case.

The most promising recent results came out of Boston. The public preschool program there boosted high school graduation rates and college enrollment, as well as SAT scores, researchers noted.

On the other hand, children randomly assigned to attend the Tennessee Voluntary Pre-K program scored substantially worse on math and reading by they time they reached sixth grade than kids who lost the assignment lottery. They also were more likely to need special education and to have discipline problems.

Further clouding the matter, a large-scale analysis of the Head Start program found it provided children neither positive nor negative effects by the third grade.

Overall, public preschool programs appear to provide an advantage to literacy and math skills for kids upon first entering elementary school, but that advantage seems to fade quickly, researchers said.

“In short, the science is not settled,” the researchers concluded in their paper.

They argue that the optimistic findings from the earlier studies might not carry over to today’s programs.

Both of the preschool programs studied early on served small numbers of children, which might have allowed more personal attention on their development, researchers said.

Further, parents these days have access to a wide variety of safety-net services and child-care options that might make as much -- or more -- of a difference as a preschool program to a child’s future development, researchers said.

"At present, the best research studies make it hard to predict the long-term effects of these investments,” said researcher Tyler Watts , an assistant professor of developmental psychology at Columbia University Teachers College in New York City. “Certainly, we agree that early childhood education is an important area for public investment. Still, we cannot confidently claim that all public pre-k programs produce positive long-term results."

More research is needed on preschool programs, both to chart the success of kids who do and don’t attend them and to suss out the “active ingredients” that distinguish successful programs from those that aren’t as helpful to kids, reseaerchers concluded.

“It's imperative that we design preschool programs to uniformly promote school success, especially for children from families with low income,” Burchinal said.

"Crucially, for parents, especially those with limited financial means, access to reliable childcare is essential for workforce participation,” she added. “Equally vital are public preschool programs that not only offer dependable care but also lay a solid foundation for their children's academic success."

Rasmussen University has more on the benefits of preschool .