Years after former D.C. mayor Adrian Fenty (D) and his schools chancellor, Michelle Rhee, left office, your feelings on their tenure likely still serve as a suitable proxy for finding your place in the country’s “education wars.” Since District students just posted substantial gains on their annual standardized assessment, these debates are fresher than ever. Rhee’s and Fenty’s backers see the scores as justification for their heroes’ hard-charging approach. But that’s not the only view. Recently, Rhee biographer Richard Whitmire begrudgingly credited current Mayor Vincent C. Gray (D) for sticking with reforms he ran against during the 2010 campaign.

Gray has stayed the course. Kaya Henderson , Rhee’s successor, has done a masterful job of balancing competing groups’ interests while continuing with the serious reforms that D.C. Public Schools (DCPS) sorely needs.

But Gray’s truly unparalleled educational legacy is much bigger than serving as caretaker for his predecessor’s accomplishments. As Fenty’s and Rhee’s battles with the Washington Teachers Union attracted national attention, then-D.C. Council chairman Gray quietly led the charge to establish universal public pre-K in the District. This was — and is — a staggering achievement.

That’s because when it comes to improved outcomes, the research backing high-quality pre-K is much stronger than similar research on test-based teacher accountability systems.

For instance, consider the justly famous Perry Preschool Program in Ypsilanti, Mich. As adults, Perry students went on to earn more income and use less welfare money than did peers who did not participate. They were less likely to repeat a grade, be arrested or have children out of wedlock. They were more likely to graduate from high school. All of this adds up to less money spent on remedial education, prisons and so on. Other programs in North Carolina, Chicago and Quebec show similarly encouraging results.

No surprise, then, that pre-K investments are hot in education policy. Education Secretary Arne Duncan has spent much of the past few months barnstorming the country to whip up support for President Obama’s proposed pre-K expansion. During his travels, he’s visited states as geographically and politically diverse as Oklahoma, Georgia, Delaware and Michigan.

But when it comes to pre-K, the District’s program stands alone at the pinnacle.

One critical reason why: Like Perry, D.C.’s pre-K is a two-year program. In 2012, 92 percent of the District’s 4-year-olds were enrolled in public pre-K, along with 69 percent of 3-year-olds. Meanwhile, Oklahoma’s much-lauded program only enrolled 75 percent of 4-year-olds and no 3-year-olds. The District could skimp here, but that’s not how investments work. Instead, the District offers students more (and higher-quality) pre-K time in order to get better long-term results.

Gray made this happen. He engaged with pre-K activists, local nonprofits and the business community. Gray coordinated meetings to draft the legislation, pushed it with his colleagues and eventually introduced it before the council. While Fenty signed the final bill in 2008, he and Rhee were largely preoccupied with the K-12 system and D.C. teachers’ contract.

So, if you’re looking to explain the recent jump in D.C. students’ test scores, give D.C.’s pre-K system some of the credit. After all, some of the sharpest score increases came in the early grades — which are filled with students who benefited from Gray’s expansion of pre-K access.

I don’t know why Gray’s central role in expanding the District’s pre-K system is so often overlooked. I don’t know why he doesn’t bring it up more often. But I know that it will make a big difference for DCPS families in the future.

This won’t be the last round of improved DCPS test scores. There may be occasional slumps, but the system’s trajectory is clear. So long as the District continues improving its pre-K system, it will persuade more families to send their children to DCPS and their tax revenue to fund the system.

To be clear, this doesn’t mean that Fenty’s and Rhee’s work was unnecessary. As a result of their work, D.C.’s teaching corps is now more competent and better compensated than ever before. A great pre-K program’s academic effects won’t hold up if students go on to a failing, incompetent K-12 system. DCPS families are fortunate that they don’t have to choose.

The writer, a former first-grade teacher, is a senior researcher in the New America Foundation’s Early Education Initiative.