A disturbing cell phone video — showing a knock-down, drag-out brawl between students in Queens — is proof that city has turned a blind eye to violence in the school system, a safety agent union leader says.

The footage was captured at Richmond Hill High School on March 10, and shows countless youngsters fighting one another in broad daylight.

It was sent to Gregory Floyd, president of Teamsters Local 237, after students claimed that their cries for help to City Hall and Mayor de Blasio fell on deaf ears.

“They gave it to me because they’re fearful for their safety and they felt the city and the mayor weren’t going to protect them because they allow this type of behavior to go on,” the school union leader explained.

“They only give out warning cards,” he said.

Police officials told The Post that officers responded to a report of a female student being struck in the face by two other young women on the day the video was filmed, but there were no arrests.

Floyd claims cops are now scrambling to find out how he was able to obtain the video — because they’re worried it might make them look bad.

“The NYPD has launched an investigation to find out how I got the video,” he said. “They’re more concerned about how I got the video than protecting the children.”

In response to Floyd’s claims, Mayor de Blasio spokesman Eric Phillips told The Post that the city was in no way trying to cover up violence in the school system.

“No truth to it,” he said. “No evidence behind it. No idea where the allegation comes from.”

Additional reporting by Michael Gartland