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benefits of preschool
Katharine Stevens

“Pre-K for all” sounds great. America’s public schools are the engine of equal opportunity and giving kids the chance to get an early start by expanding public pre-K seems like a sensible idea that anyone who cares about kids would support.

Indeed, states across the country are getting on board. Forty-five now have public pre-K and state spending on pre-K has risen by nearly 300 percent since 2002, growing from $2.4 billion to almost $7 billion in 2016. Last year alone, state pre-K funding increased by $767 million and 11 states, both red and blue, boosted funding by over 25 percent.

So we know that pre-K is politically popular. But do we really know if it works?

Related: Seven things parents and teachers should know about preschool math

To investigate that question, a colleague and I recently conducted an in-depth examination of 10 early childhood programs, widely cited in support of expanding pre-K — Abbott Preschool, Abecedarian, Boston, Chicago Child-Parent Centers, Georgia, Head Start, Nurse-Family Partnership, Oklahoma, Perry Preschool, and Tennessee — and highlights of the research done on these programs’ impact.

And as we discuss in a report released last week, the picture isn’t as simple as it appears at first glance. The programs vary greatly, their results vary greatly, and evidence on pre-K’s long-term impact is much weaker than many realize.

First, a close look at these 10 well-known early childhood programs reveals that they are as different from one another as they are similar. Some targeted four-year-olds; others focused on infants and toddlers.

Related: Why Oklahoma’s public preschools are some of the best in the country

Some operated for 50 hours per week; others for just 15. Some ran for a single year; others for up to five. Some were entirely school based; others included intensive work with parents. In fact, much of the most-cited early childhood research is on programs that weren’t pre-K for four-year-olds at all.

“So does pre-K work? We don’t know — and it’s wrong question to be asking in the first place. Instead, the critical question is: what are the most effective early interventions for improving disadvantaged children’s lives?”

Second, the methods most commonly used to study the impact of school-based pre-K have crucial flaws. For example, some studies focus only on a select group of children whose parents send them to pre-K, assessing the impact of a year of pre-K on children’s test scores in the first months of kindergarten.

Children who drop out of pre-K are eliminated from these studies, so the outcomes reported are only for children whose parents sent them to pre-K and who successfully completed the full year.

Related: Into the woods: When preschoolers spend every class outdoors

When this method is used, it’s impossible to tell how much of a program’s results are because parents self-select into the program and because dropout children are weeded out of the study. And since the majority of America’s children don’t attend pre-K in the first place, findings from these studies apply only to the limited group who do.

Another kind of study compares a group of children whose parents sent them to pre-K with a group whose parents did not. Except for this difference, researchers attempt to match the two groups on other variables, like race, income, family structure, neighborhood and so forth. If the pre-K group does better in, say, fourth grade, researchers attribute that to the pre-K program because the children are “alike” based on the variables they’ve identified. But parents who send their children to pre-K are different from parents who don’t, even if their race, income and zip code are the same. So the problem with these kinds of studies is that it’s impossible to tell whether better performance in fourth grade is due to children’s participation in pre-K or to the kind of parents they have or to some combination of both.

Related: Preschool education: Go big or go home?

Third, while advocates argue that pre-K “works,” here’s the crucial question: Works to do what? In fact, the results most studies report have much less real-world importance than policymakers and the public recognize.

Research on school-based pre-K overwhelmingly focuses just on early gains in rudimentary academic skills, like recognizing letters, holding a book right-side-up, and counting small numbers.

Most so-called positive results show that kindergartners who attended pre-K are a couple of months ahead of their peers in these basic skills; in other words, children who went to pre-K know letters in September that they wouldn’t have known until, say, November if they hadn’t. But while these kinds of short-term gains in basic skills are easy to measure and look good in headlines, they aren’t what’s important.

Instead, overwhelming evidence shows that the key to children’s long-term success is a range of cognitive and noncognitive capacities like language and executive function skills, reasoning, critical thinking, problem-solving, persistence and the ability to get along well with others. Pre-K advocates claim that small gains in basic kindergarten skills lead to large gains in these essential capacities which, in turn, lead to graduating from high school and staying out of prison. But we simply have no idea if that’s true. There’s almost no rigorous research on the long-term impact of school-based pre-K. And common sense suggests that changing outcomes for at-risk children — and knowing if they’ve successfully been changed — is going to require more than raising and measuring kindergarten test scores.

Related: Child Care Crisis: State’s weak oversight puts children in harm’s way in Mississippi

So does pre-K work? We don’t know — and it’s wrong question to be asking in the first place. Instead, the critical question is: what are the most effective early interventions for improving disadvantaged children’s lives?

It turns out that the strongest research points us to other approaches, like expanding voluntary home visiting to support vulnerable families, and improving child care, where many low-income children spend thousands of hours in the earliest, most crucial developmental years of their lives.

Our current knowledge is insufficient to justify a big expansion of pre-K as the best path forward. And the growing pre-K push may do more harm than good by diverting attention and scarce resources from more promising strategies for helping the children and families who need it the most.

Katharine Stevens is a research fellow in education policy studies at the American Enterprise Institute, specializing in early childhood education.

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