Mayor Bill de Blasio announced on Thursday that he’s ordered cops to stop arresting or summonsing Big Apple students “whenever possible” for a host of crimes — such as boozing, smoking pot and vandalism — in city schools.

Controversial Schools Chancellor Richard Carranza went so far as to say cops shouldn’t necessarily bother doing their jobs in schools.

“We have now changed the presence of policing in our schools. Police should enforce the law — they shouldn’t enforce the law in schools as a matter of course,” he said.

Rowdy pupils will also skate on spitting, harassment, trespassing and other “low-level offenses” as long as school administrators can “safely” handle the incidents, according to a memorandum of understanding that City Hall, the Department of Education and NYPD inked on Wednesday.

The kid-glove treatment outraged one high-ranking police source, who said the policy will keep parents in the dark while allowing kids to get away with crimes on campus that they wouldn’t elsewhere.

“You should be accountable for your actions. When daddy gets a pot summons in the mail, maybe that’s a way of telling them what’s going on. With two parents working, they probably don’t know. Now no one will know anything,” the source griped.

“They can get arrested for doing graffiti out in the street but they can do it in school? That’s no lesson.”

NYPD Schools Chief Reuben Beltran said parents will still be notified if a student gets in hot water.

An employee at Brooklyn’s troubled Progress High School said the move is good for students — but also a cynical effort by the de Blasio administration to artificially deflate the appearance of crime in Big Apple schools.

“I have mixed feelings — my first reaction is obviously it’s great, because it reduces the school-to-prison pipeline. On the other side, I feel like it’s a way of manipulating data,” said the source, who noted Progress HS has been handing out “warning cards” for low-level infractions as a testing ground for the new policy.

“If you look at the infraction, the things [students] would get suspended for in the past are now being issued warning cards — and so it skews your data,” the educator said. “If I’m a new principal and you leave it up to my judgement, am I going to be inclined to give that student a suspension and raise my numbers — or am I going to be inclined to make it a mandatory guidance conference? You now give me, an administrator, the ability of continuing to low-ball my numbers by leaving it up to me.”

The new policy updates a 1998 agreement strongly backed by then-Mayor Rudy Giuliani which brought school safety under the NYPD’s purview after a series of scathing reports by then-Schools Investigator Ed Stancik exposed inept security guards, cover-ups of sex crimes and wrongdoing by school custodians.

“That memorandum of understanding is from the Rudy Giuliani days. We are long passed the Rudy Giuliani days of New York City. This is a new city,” City Council speaker Corey Johnson cheered Thursday.

Under the new deal, cops can still ticket or arrest pupils for low-level offenses such as pot-possession, but it’s largely left up to the discretion of school administrators and responding officers, though Beltran struggled during a press conference Thursday to quantify how much weight would trigger police action.

“There’s a little bit of judgment involved in that, because you can quantify, the containers come different when it comes to marijuana — sometimes it comes in candy form, sometimes it comes in bags and smokable forms. But we’ve been using, if it’s three or more, then they would get a summons, depending on the circumstances, depending on the age and everything else,” he said, adding, “if it’s one bag, if it’s a very large bag, then the person would not be qualified for the warning card.”