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According to the National Institute For Early Childhood Research, nearly half of all 3-year-olds and a third of all 4-year-olds in the United States were not enrolled in preschool in 2019. That's in large part because many parents can't afford it. Imagine a future where we changed that. A future where every American child had access to two years of preschool during a critical period of their mental development. How would their lives change? How would society change? If President Biden gets his way, and Congress agrees to spend $200 billion on his proposal for universal preschool, then we may begin to find out.

But it turns out, we kind of already know. In fact, a new study from the National Bureau of Economic Research gives us a glimpse of what that world could look like. It adds to a burgeoning amount of high-quality research that shows just how valuable preschool is — and maybe not for the reasons you might think.

An accidental experiment

The story begins back in the mid-to-late 1990s. The Mayor of Boston, Thomas Menino, wanted to improve the city's schools. One of his big goals was to provide universal, full-day kindergarten for Boston's kids. But the budget was tight, and following a task force's recommendations, he and local lawmakers decided to move resources from preschool (for 4-year-olds) to kindergarten (for 5-year-olds) in order to achieve it.

The result was an even more limited number of slots for city-funded preschool, and the city officials had to figure out how to fairly divvy up those slots. They resorted to a lottery system, randomly selecting kids who would get in.

Fast forward two decades later, and the economists Christopher R. Walters, Guthrie Gray-Lobe and Parag A. Pathak saw this as a golden opportunity to see how preschool can affect people's lives. The fact that Boston's school administrators randomized who got admitted meant there were two virtually identical groups of kids with only one difference: one group got an extra year of education by going to preschool. That gave the researchers the opportunity to compare and contrast the two groups of kids and credibly see how kids' lives changed as a result of getting into preschool.

About 4,000 4-year-olds took part in Boston's preschool lottery between 1997 and 2003. Walters, Gray-Lobe, and Pathak acquired data on them from the Boston school system. And then they were able to get additional data from other sources that gave them insight into ways that the children's lives might have benefited from an additional year of preschool education. These kids are now all twenty-somethings — a fact that should make you feel old.

Consistent with other studies that find preschool has a huge effect on kids, Walters, Gray-Lobe and Pathak find that the kids lucky enough to get accepted into preschools in Boston saw meaningful changes to their lives. These kids were less likely to get suspended from school, less likely to skip class, and less likely to get in trouble and be placed in a juvenile detention facility. They were more likely to take the SATs and prepare for college.

The most eye-popping effects the researchers find are on high school graduation and college enrollment rates. The kids who got accepted into preschool ended up having a high-school graduation rate of 70% — six percentage points higher than the kids who were denied preschool, who saw a graduation rate of only 64%. And 54% of the preschoolers ended up going to college after they graduated — eight percentage points higher than their counterparts who didn't go to preschool. These effects were bigger for boys than for girls. And they're all the more remarkable because the researchers only looked at the effects of a single year of preschool, as opposed to two years of preschool (as President Biden is now proposing for the nation's youth). Moreover, in many cases, the classes were only half a day.

Intriguingly, while attending preschool at age 4 had clear effects on these kids' entire lives, it did not improve their performance on standardized tests. These findings fit into a large body of research that suggests the true value of preschool is helping little ones to develop "non-cognitive skills," like emotional and social intelligence, grit and respect for the rules.

"The combination of findings — that we don't see an impact on test scores, but we do see an impact on these behavioral outcomes and the likelihood of attending college — is consistent with this idea that there's some kind of behavioral or socio-emotional, non-cognitive impact from preschool," says Christopher Walters, an economist at UC Berkeley who co-authored the study.

In other words, there's growing evidence that preschool can permanently improve kids' lives — but it's not necessarily because it makes them smarter. It seems more related to making them more disciplined and motivated, which is just as important (or perhaps even more important) for their future livelihoods as how well they perform on reading or math tests.

The bigger picture

This latest study isn't the first to show the outsized effects of providing a preschool education. The Nobel Prize-winning economist James Heckman has spent many years studying the results of small, randomized experiments with preschool in the 1960s and 1970s. The most famous such experiment was The Perry Preschool Project, which was conducted in Ypsilanti, Mich. The program provided two years of high-quality preschool for disadvantaged 3- and 4-year-olds.

Heckman and his colleagues found that the Perry Preschool had seismic effects on the kids who participated. They were much less likely to get arrested, go on welfare or be unemployed as adults. They earned significantly more. In a recent study, Heckman and his team found that even the kids of the kids who went to the Perry preschool had significantly better outcomes in life.

All in all, Heckman and his team estimate that every dollar the Perry Preschool project invested in kids had a return on investment of 7-10% per year, through increased economic gains for the kids and decreased public spending on them through other social programs when they got older. That's a substantial return, equal to or greater than the average annual return from the stock market, and much greater than most other things our government spends money on.

Other preschool programs studied by Heckman and his colleagues have had even greater benefits. In the 1970s, a couple of programs in North Carolina experimented with high-quality childcare centers for kids. The centers offered kids aged zero to five education, medical checkups, and nutritious food. Heckman and his team found these centers delivered a 13 percent annual return on investment to the public for every dollar they invested. The program helped Heckman develop what's known as "the Heckman Curve," which asserts that the government gets more bang for the buck the earlier it provides resources to educate people. Educating toddlers, Heckman says, is much more powerful than educating high-schoolers, college students, or adults in, for example, job-training programs.

As astounding as Heckman's findings about preschool have been, naysayers have long questioned whether such effects could be replicated with larger scale programs, like the one President Biden is now proposing. This new study out of Boston, which looks at a large-scale program conducted across the entire city, is another brick in the growing edifice of evidence that shows preschool is a worthy investment, not just for kids, but for society overall.

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