Mayor Bill de Blasio was personally alerted to evidence of grade-fixing and fraud at Maspeth High School in mid-August, but ignored pleas to remove the school’s allegedly crooked leaders before the new school year, The Post has learned.

“It was like I had witnessed a crime,” said City Councilman Robert Holden, who demanded to speak with the mayor after meeting whistle-blowing teachers with documents showing a culture of cheating at the highly rated school.

“I wanted him to put it on the fast track. I wanted him to step into this and get those people out,” the Queens lawmaker told The Post.

But the mayor did not act with urgency, Holden charged, prompting him to go public and to meet with acting Queens District Attorney John Ryan, who has launched an investigation.

Maspeth HS, awarded a National Blue Ribbon in 2018 for a near-perfect graduation rate, enforces an unwritten “no-fail policy,” even when kids do little or no work, eight teachers have told The Post.

Assistant principals strong-armed faculty members into passing students no matter what, they said. Some teachers helped kids cheat on Regents exams or fixed wrong answers. Failing grades were changed to a passing 65, which kids call the “Maspeth Minimum.”

Even chronically truant, drug-addled students got diplomas — some of them pushed out the door months early, as former student Thomas Creighton and his parents came forward to confirm. But last week his father, Daniel Creighton, said the family had not heard from any investigators.

“If that doesn’t prove there’s no urgency, I don’t know what does,” Holden said. “Not only did they steal city money meant to provide services, but they stole the education from these students.”

The city Department of Education has said only that it will investigate the allegations.

Principal Khurshid Abdul-Mutakabbi, who remains at Maspeth’s helm, has not addressed his faculty to discuss the probes or a series of Post exposés.

The stunning allegations surfaced on July 30, when Holden first met a Maspeth teacher who brought him a binder full of evidence, including schedules with non-existent classes, records of no-show students who graduated, and statements by students who said they received passing grades or test scores they didn’t deserve.

Holden called the mayor’s office immediately. On Friday, Aug. 2, he met with Lydon Sleeper, the mayor’s intergovernmental affairs director, asking him to bring in the city’s Department of Investigation.

Holden then forwarded the evidence to DOI, which sent it to the Special Commissioner of Investigation for city schools, Anastasia Coleman.

The next week, four ex-Maspeth teachers came to Holden’s office to speak with investigators, but SCI said it had no one to send.

Coleman, whose SCI office is independent, handed off the academic-fraud allegations to the DOE’s own investigative office, which falls under the mayor’s office.

After two weeks, when no investigators had contacted him, Holden emailed de Blasio on Aug. 13, a day after the mayor returned from Iowa for his now-defunct presidential campaign.

The subject line: “Need to talk.”

The mayor called back the following evening. Holden went over the litany of alleged misconduct at Maspeth HS, including grade-fixing, Regents rigging, fake classes to give students credits toward graduation, and intimidation of teachers who didn’t play ball.

“They’re gangsters,” Holden said he told the mayor. “They should not be in there one more day.”

But de Blasio seemed more concerned about Holden, a fellow Democrat, going to the press.

“It’s good that you gave it to me, but if you want to be on my team you have to play like a team member,” Holden quoted him as saying.

The mayor noted that Holden was fortunate to speak with him. “You have your district. I have to run the whole city. I’m the big leagues.” he said, according to Holden.

“I just kept saying, ‘Maspeth High School needs attention,’” Holden said.

Classes started Sept. 5 without any sign of attention. The Maspeth whistleblowers finally asked to meet with a reporter, Holden said.

Three days after a front-page report in the Post on Sept. 15, two DOE investigators met with Holden but had yet to start work on the case.

Since then, more Maspeth teachers, former and current, have contacted The Post to back up the first whistleblowers. Some turned over additional documents such as class schedules showing teachers listed as holding two or three classes in the same time period.

Another schedule lists an assistant principal as the teacher of “Intro to Journalism” during period “OO” — before the school day starts at 8 am — while he coached baseball.

“Those are not real classes,” an insider said, explaining that kids don’t have to show up on a regular basis but may get “packets” of worksheets to do on their own. Incomplete or inadequate work could still result in a passing grade and credit, teachers said.

One student’s daily schedule lists 11 classes, including three during period 00 — Intro to Journalism 2, Topics in Health, and Participation in Government — plus US History, Astronomy, Economics, Geometry, English composition, art and phys-ed.

Truant or failing students are “loaded up” with bogus classes they need on their transcripts to graduate, the teacher said.

“They’re robbing students of the chance to learn how to bounce back, ” another said. “A lot of kids just stop trying when they realize they will never be given a failing grade.”

City Hall spokeswoman Jane Meyer said in response, “Immediately after the Council Member brought these allegations to our attention this summer, we reported them to SCI and have since followed up multiple times. An investigation is ongoing and if any improprieties are confirmed to be true, immediate action will be taken.”