The current field of presidential candidates loves talking early education. Big K–12 policy ideas are in short supply, but every major candidate looking to challenge the president in 2020 favors moving towards universal pre-K across the country.

This is largely because, done right, early education investments appear to be able to advance children’s development and improve their long-term social, academic, and economic trajectories. What’s more, these programs are relatively uncontroversial. In 2017, a First Five Years Fund poll found that “89% of voters support making quality early education for children from birth through age five, including child care, more affordable for working families.” This sort of public enthusiasm is unheard of in education policy. After almost two decades of public battles over rising academic standards, assessments, school and teacher accountability, school choice, and more, it’s no wonder that politicians are eyeing greater investments in early education as something everyone can agree on.

But while expanding and improving pre-K education is more politically palatable, it’s complicated to design and implement programs in ways that deliver equitable benefits for children. Politicians’ rhetorical excesses can sometimes obscure the challenges of building early education programs that grant universal access while providing truly impactful levels of quality for all children. For instance, a 2017 meta-analysis of the state of research on pre-K found sufficient evidence to warrant the “continued implementation of scaled-up pre-k programs,” but warned that “Pre-k programs are not all equally effective.”

Fortunately, there are examples of large-scale public investments in pre-K that can serve as design and implementation models for future early education expansions. As I’ve recently written for the New York Times and Vox, Washington, D.C. runs a comprehensive, high-quality universal pre-K program that could be a model for the rest of the country.

What Makes a Good Pre-K Program?

If you ask Zauraya, a pre-K student at Turner Elementary—a school in the DC Public Schools (DCPS) system—what she does in pre-K, and she’ll tell you, “I play all day.” Dallas, one of Zauraya’s classmates at Turner, says that his favorite part of pre-K is the table in his class where students play with “the [toy] train tracks . . . [because] my mommy works at the train station.”

Zauraya and Dallas think of their school days as time to explore and imagine with their classmates. If train tracks and playtime don’t sound very academic, note that one commonality among high-quality pre-K programs is that they aim to introduce children to the basic social skills they will need later to thrive in school. They help students learn to participate in a structured learning environment—following routines, building knowledge over a period of time, collaborating with peers, and much more.

These so-called “noncognitive” skills are the foundation of school readiness. And they’re essential to academic development. “[Pre-K is] not as much explicit literacy instruction as you might think,” says former Turner Elementary principal Eric Bethel. “It’s really a lot about language development . . . hearing, internalizing words, and then speaking.” That is, it’s about knowing how to engage in conversation, think critically, and contribute to a learning environment.

As kids learn to work together, they talk, listen, process, engage, plan, and generate new ideas. This builds towards academics: as children learn to use language, they begin growing other early literacy skills—figuring out that words are made up of sounds, finding that symbols on pages can represent sounds and words, learning how to hold books that contain these symbols, and the like. This is why these noncognitive skills appear to be central features of quality pre-K programs that can raise kindergarten readiness, close academic achievement gaps, reduce special education placements, raise children’s future incomes, lower the likelihood of incarceration, and much more.

The benefits of high-quality pre-K programs, then, seem to deserve the praise they’re getting on the campaign trail. But that’s not necessarily the whole story. A number of studies have found that, while pre-K programs often show strong and positive academic impacts on children as they leave for kindergarten, these effects “fade out” over time. Often, several years into elementary school, students who attend pre-K no longer appear to be doing better, on average, than students who did not attend pre-K.

Pre-K programs can advance educational equity and improve children’s outcomes, but it’s no simple matter to ensure that those gains last.

This hints at a thorny problem for policymakers: there is less consensus in the field about the contours of quality early education programs and their ultimate objectives than is often acknowledged. Pre-K programs can advance educational equity and improve children’s outcomes, but it’s no simple matter to ensure that those gains last.

What the D.C. Experience Says about Setting Goals and Continuously Refining Practices

If you’re familiar with early childhood education’s history in American politics, you can understand the desire to aggressively sell pre-K’s effectiveness. In the decades since the United States built and dismantled its World War II-era early education investments, pre-K has been out in the political cold. Given that some studies suggest a wide range of benefits to these programs, why not use that research to sell them to the public?

But there are unintended consequences of treating pre-K as a cure-all. Above all, it sets a difficult, complicated bar for measuring and determining success. Is it enough for a pre-K program to simply prepare children for kindergarten? After all, we measure most elementary and secondary school classrooms by how well they prepare students for the next grade. Or, is a successful pre-K program one that raises early literacy scores? Or high school graduation rates? Or long-term tax revenues on higher adult incomes? In essence, if pre-K backers promise the moon, it risks making even largely pre-K program look unsuccessful. “There’s this constant need to justify the investment when in reality we don’t have any agreement on what success of the investment actually is,” says early education data expert Elliot Regenstein. “Part of what we have to do as an early childhood advocacy movement is to be upfront about what it is we are and are not selling here.”

In response, many pre-K programs measure quality against program “inputs.” These include things like funding amounts, staff credentials, adult-child ratios, daily schedules, and the like. In theory, these metrics serve as proxies for positive student outcomes. Washington, D.C.’s pre-K program scores well on nearly all of these. On the National Institute for Early Education Research (NIEER) scorecard tracking state pre-K programs, D.C. ranks first in the country on funding and family access. D.C. spends about as much on its pre-K program as Maryland, Ohio, and Minnesota spend, combined. In a country where full-day kindergarten is not yet a universal expectation, D.C. pre-K runs for a full day (at least 6.5 hours) for a full 180-day school year. This sort of comprehensive programming is helping families—recent research from the Center for American Progress found that D.C.’s pre-K program is helping mothers get back to work after having a child.

The D.C. pre-K system is inputs-rich, but the research linking these data to student outcomes (in D.C. or other large, public pre-K programs) is often thin. For instance, a 2015 National Academies of Sciences, Engineering, and Medicine report on early educators recommended that policymakers build toward requiring all pre-K teachers to have at least a bachelor’s degree, despite noting that “empirical evidence about the effects of a bachelor’s degree is inconclusive.”

Instead of measuring pre-K quality inputs as a foundation for better student outcomes, then, policymakers could simply measure the student outcomes themselves.

Instead of measuring pre-K quality inputs as a foundation for better student outcomes, then, policymakers could simply measure the student outcomes themselves. It’s a simpler equation: pick some outcomes that pre-K should improve, and then see whether pre-K graduates do better on those. Unfortunately, there’s little field consensus on which outcomes we should measure when determining if a pre-K program is “high-quality” or “effective.”

For instance, some of the studies finding that pre-K’s academic benefits fade after several years also find that pre-K attendees still gain long-term advantages—they earn more as adults and/or are less likely to rely on social assistance programs or wind up in prison, for instance. That is, in some studies, pre-K programs appear to help kids right away, only for the effect to vanish, and then reappear in adulthood. The Upjohn Institute’s Tim Bartik explains: “This fading and reemergence of effects could be due to noncognitive skills, which are important to adult earnings but harder to measure using standardized tests.” These skills—things like motivation, persistence, and effective interpersonal interaction—are what Zauraya and Dallas are training in as they work their way through the day in their pre-K classrooms.

In other words, even if we focus on measuring particular student outcomes in an effort to define what constitutes “high-quality” and/or “effective” pre-K, it’s not clear that we know precisely what we should be measuring (or how to do it). Different pre-K programs deal with the problem in different ways. Many, like D.C.’sand San Antonio’s—use observational tools that measure how well their classrooms support children’s development across a range of indicators.

This is why one of the big things that Washington, D.C. gets right when it comes to universal pre-K is largely unnoticed. It tinkers. It keeps reworking its classrooms and puts significant energy toward raising instructional quality. There’s some evidence that this is working. As I noted in my recent New York Times piece,

In 2018, the school district reported that fewer than half of 3-year-olds were meeting early literacy benchmarks when they arrived in pre-K classrooms. However, 86 percent were finishing pre-K ready for kindergarten on the cognition skills measured by the city’s early childhood assessment—and 83 percent were becoming kindergarten-ready on language metrics. More than 75 percent reached kindergarten-ready skills on fluently matching sounds with letters.

“Incremental improvements over time compound in a very positive way, just like investments,” says Jack McCarthy, the president and chief executive of the public charter school network and research and development institute, AppleTree, “If you’re only in it for the short term—we should all be impatient, and you can look at the long game while still having a sense of urgency—but we should be patient.”

AppleTree began running pre-K classrooms in the early 2000s, and, over time, developed an early learning curriculum. With federal funding support, it built this into a replicable high-quality model that is in use in a range of charter pre-K classrooms across the city. This iterative development process helped AppleTree define program quality and steadily align its practices to pursue it.

In the DCPS school district, leaders have focused on developing adult learning materials for their pre-K teachers. These are delivered and facilitated by pre-K coaches, who work one-on-one with DCPS’ approximately 400 pre-K teachers to identify key areas for improvement. Bethel, the Turner Elementary principal, says that his school’s pre-K coach has helped him “narrow my instructional lens and help me be able to help [pre-K] teachers.” Cheryl Ohlson, the interim deputy chief of DCPS’ Early Childhood Education Division, says that this systemwide commitment to continuously improving quality is an untold story of D.C. pre-K.

And perhaps there’s a reason that it’s untold. It’s hard to rally public support around a pitch like: “pre-K can help improve educational and life outcomes for many children, so long as we fund it well, and implement it carefully over a long period of time, while constantly adjusting its model.” It’s not snappy enough for a stump speech. And that’s okay, so long as leaders remember that the work of selling universal pre-K is just the first step in building it.