Researchers have known for a while that early childhood education helps build decision-making and social skills.

Yet just over a third of 4-year-olds in the U.S. attend preschool. Access to public preschools is spotty and varies by state, city and income level.

But a study published this week by the National Bureau of Economic Research makes the case that expanding early childhood education could be well worth the investment.

Attending preschool is a big positive for kids, per Sara Amadon, a senior research scientist at Child Trends.

“We’ve kind of seen more persistence in school, better test scores, higher graduation rates,” she said.

Even better-paying jobs decades down the line — “something in the area of about 5% higher earnings,” said Randy Akee, a professor of public policy and American Indian studies at the University of California, Los Angeles. He co-authored the NBER study.

Akee used data from a lottery-based preschool for Indigenous students. Lots of families applied to the preschool; some got in and some didn’t. The hardest part of the investigation came a quarter-century later.

“To find the students themselves in adulthood, track them down, would be quite costly,” Akee explained.

But he was able to match the students’ data with their adult earnings using info from the IRS and compared the two groups. He found that attending preschool raised students’ incomes across the board.

“Some of the largest results are for girls who come from below median household income,” said Akee. “So preschool has the ability to reduce inequality, reduce unequal outcomes even later in life.”

That means more kids should be attending, said Anna Johnson, who researches family policy at Georgetown University.

“In terms of positive investments in young children’s well-being, public preschool — I just don’t think you can get better bang for your buck,” she said.

Public preschools are expanding nationwide, but they’re bumping up against another issue: a shortage of early childhood educators.