High school seniors who missed more than six weeks of class would still receive their diplomas under an emergency measure approved by the D.C. Council, even as the city remains mired in a graduation scandal.

The measure, which passed Tuesday on a 12-to-1 vote, would apply only to students who meet all other academic standards.

Council members David Grosso (I-At Large) and Robert C. White Jr. (D-At Large), who ­co-introduced the legislation, said the school system started enforcing long-ignored attendance policies in the middle of the year, amid the graduation imbroglio. They said it is unfair that students have to pay the price for the city’s mistake.

The vote sets up a potential showdown between the council and Mayor Muriel E. Bowser (D), whose signature is necessary for the reprieve to go into effect. Bowser’s administration has said it opposes the measure, and council member Brandon T. Todd (D-Ward 4), a Bowser ally, cast the lone vote against it.

When asked whether the mayor would sign the measure, her office said she is reviewing her options and referred to an emailed comment from the city’s deputy mayor for education that sharply criticized the legislation. ­Bowser, who is seeking reelection this year, has not vetoed a bill since taking office in January 2015.

A spokesman for D.C. Public Schools, whose chancellor is appointed by the mayor, said school leaders are also against the legislation.

The council passed the reprieve on an emergency basis, meaning it will be implemented on an expedited timeline and does not require congressional review, unlike standard D.C. measures.

“This emergency legislation undermines [the school system’s] efforts and sends a troubling message about the importance of school attendance, suggesting that students need a waiver to excuse absences,” Ahnna Smith, the interim deputy mayor for education, said in a statement. “We will continue to stress the importance of attendance because every day counts.”

City policy dictates that students who have 30 or more absences in a class should fail, and the proposed legislation would delay stringent enforcement of the attendance policy until the 2018-2019 academic year.

“There are students who were operating under attendance policies articulated to them by their schools,” White said. “They should not be the scapegoat for a misstep” by D.C. Public Schools.

Several council members expressed misgivings about the legislation Tuesday before voting for it.

“The optics in which you have the council stepping in and saying, ‘Well, kids can miss 30 days and it’s okay,’ ” council Chairman Phil Mendelson (D) said. “And it’s kind of, as I said, no good decision either way.”

Data released last month shows that 64 of the school system’s 3,623 seniors could receive a break because of the legislation. Those students are at risk of not graduating for one reason: They have too many absences.

But White said the school system has updated its figures, and it’s now believed 26 seniors would be affected by the legislation. It is unclear why that number changed, but White suggested that schools may have discovered some students in danger of not graduating had failed to meet other academic standards.

A D.C. schools spokesman said the number of students the legislation will affect is not final.

The measure would also apply to students in lower grades who are at risk of not advancing to the next grade because of absences, according to Grosso’s statement.

The Class of 2017 posted a 73 percent graduation rate — a record high for the city.

Data released by D.C. Public Schools last month indicates that 46 percent of seniors are on course to cross the graduation stage. Twenty-one percent, or 758 students, are considered moderately off track.

Earlier this month, teachers at Roosevelt High in Petworth told The Washington Post that students’ attendance records had been altered in recent months to erase absences — a breach that could have allowed chronically absent seniors to graduate.

The school system said an investigation into those allegations continues.