Fewer high school seniors in the District are expected to receive diplomas in June than in the year before, a sharp reversal for a school system that had celebrated a 20-point increase in its graduation rate since 2011.

Data released Thursday by D.C. Public Schools shows that 42 percent of seniors attending traditional public schools are on track to graduate, while 19 percent are considered “moderately off-track,” meaning they could still earn enough credits for a diploma.

The likely drop in the graduation rate is the latest fallout from an investigation that cast doubt on the validity of diplomas awarded last year. The graduation rate in 2017 was 73 percent, but the probe revealed that one in three graduates received their diplomas in violation of city policy. Those students had walked across graduation stages despite missing too many classes or improperly taking makeup classes.

Even if all of the students regarded as “moderately off-track” receive diplomas, the graduation rate would stand at about 61 percent — 12 points below last year’s.

D.C. graduation rates reflect the percentage of students who receive their diplomas in four years. Twenty-six percent of students who started their freshman year with the class of 2018 have withdrawn or transferred out of the system. The city still needs to determine how many are in each category.

After the investigation into the 2017 graduation rate, the school system promised to stringently enforce long-ignored attendance policies, which state that students should fail a class if they are absent more than 30 times in a school year.

The report portrayed a systemic culture in which teachers felt pressured to award diplomas even if teens failed to meet requirements, all in the name of improving graduation rates.

This is the first year the city has released graduation data months before diplomas are awarded, so it is unclear how the numbers compare to previous years.

For Mayor Muriel E. Bowser (D), the rates came as no surprise.

She said in an interview Thursday she had expected the decline after the city-commissioned investigation.

“We should have all expected it,” Bowser said. “These are the truest numbers we’ve had related to grades, attendance and graduation.”

Council member David Grosso (I-At Large), who chairs the Education Committee, said the midyear data allows the city to understand how much work needs to be done.

“It’s bad news that there are so many kids struggling,” he said, “but it’s good news that we are being honest about it, and I think there’s some value to that.”

The figures show that a majority of seniors at many comprehensive high schools are not on track to graduate.

At Anacostia High, the school with the smallest percentage, only 19 percent of seniors have passed or are passing the classes required to receive their diplomas.

Twenty-five percent are considered “moderately off-track,” meaning they are failing one or two courses but can earn credits through summer school or credit-recovery programs.

At Ballou High — the school at the epicenter of the district’s graduation scandal — 27 percent of seniors are on track to graduate.

Wilson, the city’s highest-performing comprehensive high school, has 56 percent of students on track to receive their diplomas.

The District’s magnet and application schools show much higher expected graduation rates. At Banneker High, 82 percent of students are passing or have passed all courses required for graduation.

The school system also released data Thursday showing the status of students’ attendance records about three months before graduation.

At Ballou, 14 percent of seniors already have accrued 30 absences in a class, which automatically earns a failing grade — the highest rate of any comprehensive high school. At Anacostia, that figure is 13 percent. These students won’t be able to graduate by the end of the school year.

Nearly every senior at the two schools, according to the data, has met with a counselor or administrator, and most parents have met with a school employee about their children’s graduation status.

Bowser said Thursday that while District schools have burnished their academic and extracurricular programs, students need to show up to reap the benefits — something that is not happening.

Across the District’s high schools, 18 percent of seniors accrued more than 10 absences in a single course during the second quarter, earning them failing grades. Nine percent of seniors have more than 30 absences.

The school system said it released the data to be transparent.

“We want to make sure that every graduate going forward has truly earned their diploma,” said Michelle Lerner, a spokeswoman for the school system. “We’re focused on making sure that the students who have graduated have earned their diploma and the community feels that way as well.”