D.C. Mayor Muriel E. Bowser (D) discusses a schools review in January. (Jahi Chikwendiu/The Washington Post)

Mayor Muriel E. Bowser (D) is running for reelection as the city’s public schools are reeling from scandals, undermining some achievements touted during a decade of high-profile reform efforts in the city.

An investigation earlier this year found that one in three graduates in 2017 received diplomas they did not earn — thereby inflating the school system’s graduation rate — while another probe discovered residency fraud among 30 percent of the student body at Duke Ellington School of the Arts.

But Bowser, who faces no serious challengers in the Democratic primary on June 19, is campaigning on the successes of city schools.

Last week, Bowser tweeted from an account affiliated with her campaign that “D.C. is now the fastest improving school district in the nation.” Her campaign website makes a similar claim.

“In our first term, we jump-started education reform — and D.C. is now the fastest improving school district in the nation,” she tweeted. “In our second term, #TogetherWeWill continue improving our students, teachers and schools.”

The idea that D.C. is the fastest-improving urban district in the nation gained steam in 2013 — more than a year before Bowser took office — when the city posted some of the country’s biggest gains on the National Assessment of Educational Progress (NAEP), an exam the federal government has administered every two years to fourth- and eighth-graders since the early 1990s.

The city’s scores had long trailed the rest of the nation.

But recently, that growth has slowed, with D.C.’s overall pace of improvement falling behind urban districts, including Miami and Chicago.

“I’ve read the NAEP scores, and they are not consistent with her statement,” D.C. Auditor Kathy Patterson said. “We are only going to move forward if there is honesty.”

Michael Hansen, the director of the Brookings Institution’s Brown Center on Education Policy, said the District’s improved performance on the NAEP test is noteworthy, but most of it occurred before Bowser took office. A decade ago, D.C. was among the lowest-ranked urban districts in the country but is now more toward the middle of the pack. The claim of “fastest improving district” does not hold true since Bowser took office in 2015, he said.

The campaign also sent out a fundraising email last week touting rising graduation rates, but Bill Lightfoot, Bowser’s campaign chairman, said that was sent in error.

The city reported years of record graduation rates, including 73 percent in 2017. But that statistic has been called into question after a city investigation revealed that one in three graduates received their diplomas despite missing too many classes or improperly taking makeup classes. Administrators told investigators they felt pressure to make sure students passed classes needed for graduation.

School officials expect a drop in graduation rates this year, with school leaders saying only students who meet attendance requirements will receive diplomas next month.

Lightfoot said the mayor’s statement was referring to the whole education system, including investments in infrastructure and vocational training, not just test scores.

“Her view is that it’s not just about test scores,” Lightfoot said. “You have to look at the totality of the circumstances and the education system. When you put it all together, that is the basis of the statement.”

Matthew Chingos, the director of the Urban Institute’s Education Policy Program, said Bowser’s claim is not entirely wrong. He said when looking at NAEP scores over the past decade, D.C. has made some of the biggest gains, particularly in fourth grade. But there has not been standout growth since the gains in 2013.

“If a politician is out there saying the District is the fastest improving in the country, there’s some basis to that, but of course there’s more nuance to it,” Chingos said. “If I’m [Chicago Mayor] Rahm Emanuel, I’m saying that Chicago has had the biggest change since 2009 in eighth-grade math.”

Catharine Bellinger, the D.C. director for Democrats for Education Reform — which has long supported the city’s reform efforts — said misleading claims hurt the city’s credibility. To improve, the city needs to be honest about its shortcomings, she said.

“We can still be proud, we can still say that we made progress,” she said. “We need to focus on the changes that are still necessary. It’s not helpful to rest on our laurels.”