Now that the Queens District Attorney’s Office is investigating the apparent fraud behind the remarkable success of Maspeth High School, we have to ask: Why did no one at the city Department of Education start asking questions first?

Maspeth’s virtually perfect graduation rate, even for special-ed students, should have invited scrutiny. But it seems no one stood up to suggest copying the magic that produced those results — nor to ask if the results were faked.

Teachers shouldn’t have had to go to The Post and to City Councilman Robert Holden to blow the whistle.

“They Cheat,” Susan Edelman’s exposé Sunday, has the ugly facts.

In 2018, 99% of Maspeth kids graduated on time, against a citywide rate of 76%. And all received a Regents diploma or the more-desirable advanced Regents diploma — with even every special-education student managing a Regents.

But four teachers told The Post that the secret sauce is cheating — on a wide scale. Top administrators enforce what the kids call “the Maspeth Minimum” — you literally aren’t allowed to notch a failing grade, if you routinely don’t do the work or even show up.

Assistant principals “teach” classes that don’t even meet in order to hand kids fake course credit. Some teachers allegedly gave out the answers during Regents testing.

Grades change magically; proctors completely overlook blatant copying of other students’ test answers.

And teachers pay if they don’t play along: They “face ‘retaliatory’ evaluations or trumped-up disciplinary charges — and fear losing their jobs — if they don’t cooperate,” the whistleblowers said.

If “you are called in about kids who are failing, the message is, ‘Make sure you pass them [even if] you have to change the grade,’ ” they told Edelman.

See cheating? “If you bring it to the dean, nothing happens. Discipline is laughable. There’s no consequences for misbehavior, for disrespecting teachers or for cheating.”

A diploma based on fraud isn’t a gift. It represents the theft of the education every child should receive — letting administrators look good at students’ expense.

Maspeth’s miraculous-seeming results won the school recognition from the state and federal Education Departments. But it’s not those bureaucrats’ job to police school administration — that’s up to the city DOE.

Yet the DOE time and again has failed to get on top of a cheating scandal until after The Post exposes it. You have to conclude that the central office just doesn’t want to know.