D.C. Mayor Muriel E. Bowser launched an investigation Wednesday into allegations that some students who were chronically absent and others who could scarcely read and write were allowed to graduate from Ballou Senior High School in Southeast Washington.

The D.C. Council also announced that following the accusations, it plans to hold a hearing to investigate graduation rates in the city.

At a midday news conference, Bowser and D.C. Public Schools Chancellor Antwan Wilson said they are taking the allegations seriously but stood by Ballou — a historically low-performing high school that has been touted for its seemingly rapid improvements in recent years — and its principal.

“We think these are extremely important and concerning allegations,” Wilson said. “At this point, to be honest with you, I don’t know what mistakes were made at Ballou.”

The allegations surfaced in an article published Tuesday by WAMU and NPR that said that the school gave diplomas to seniors who did not meet graduation requirements and that administrators pressured teachers to pass students.

The article portrayed an environment of dysfunction at the high school, reporting that students were irresponsibly pushed toward graduation, which left them unprepared for college and the workforce.

Bowser and Wilson did not provide specifics of what the review will entail, but they indicated it would look at citywide graduation policies and whether teachers and leaders at Ballou adhered to graduation standards.

Bowser said there will be two investigations — one led by the Office of the State Superintendent of Education that will be completed within 45 days and the second spearheaded by two deputy chancellors, who will begin reviewing all D.C. schools starting immediately.

Wilson said he wants to determine how pervasive these issues are at Ballou.

According to Bowser, the citywide investigation will look into adherence to attendance and graduation policies throughout the District.

The review will explore whether the District should “make [the policies] clearer for all parties involved — teachers, principals and parents — and more transparent.”

The WAMU account marked a sharp departure from the laudatory headlines Ballou received earlier this year, when each of its 190 senior students, who are overwhelmingly black and from low-income backgrounds, applied to college and were accepted.

Bowser and Wilson did not challenge the conclusions of the WAMU article, although they said there are other indicators — including improved standardized test scores — suggesting that the school is successful.

Wilson said he had been impressed with Ballou’s principal, Yetunde Reeves, and her work during school visits and that he intends to keep her in her post.

The school posted a graduation rate of 64 percent in 2017, up from 50 percent in 2012. The school also showed steady improvement on its Partnership for Assessment of Readiness for College and Careers (PARCC) scores, a standardized test.

Test scores from 2016 showed that 8 percent of students met or approached meeting standards in math and that 9 percent met or approached standards in English.

In 2017, those numbers increased to 10 percent in math and 22 percent in English.

Still, those results fell well below the average scores for the District, with 51 percent of students meeting or approaching meeting standards in math and 53 percent in English.

“I personally believe Principal Reeves should be renewed based on my visits with the school,” Wilson said. He added that he has no “evidence that it’s true” that students graduated unable to read or write.

Low-performing schools, such as Anacostia and H.D. Woodson high schools, recorded impressive graduation gains in 2017. Anacostia had a 17 percent increase in its graduation rate between 2016 and 2017.

“We will thoroughly review our policies related to attendance, graduation and credit recovery,” Bowser said.

“I have directed our Office of the State Superintendent of Education, which is our state education agency, to review those policies and compliance with those policies and turn around a report to us in the next 45 days.”

Council member David Grosso (I-At Large), who chairs the D.C. Council’s education committee, said the panel will hold a public oversight hearing Dec. 15.

“I am deeply disappointed to hear reports alleging that students at Ballou High School were not eligible for graduation but still received a diploma,” Grosso said in a statement.

“If students are able to graduate school in light of chronic absenteeism and without producing the appropriate work product, then we are not fulfilling our mission to put them in the best position to succeed in life.”

The WAMU-NPR report found that a majority of Ballou’s 2017 graduating class missed more than six weeks of school. D.C. school policy dictates that students will fail a class if they are absent 30 times.

Educators interviewed by WAMU said that teachers were pressured to pass students and that students were aware that expectations weren’t high for receiving a diploma.

The school system does not expect to rescind any diplomas, regardless of the outcome of the review, Wilson said.

The chancellor encouraged students and teachers who are concerned about the allegations to reach out to the school system. He also said no teacher should feel pressured to pass students and they should speak up if they do.

“The grade that they give students, I do not expect it to be anything other than what they earn,” Wilson said.

“That’s extremely important.”