Bonehead boys at fancy NYC prep school set up fake border-patrol checkpoint in lobby, ask to see students’ ‘papers’ — as mariachi band plays

Knucklehead preppies at Manhattan’s elite Collegiate School last week pulled a senior prank by setting up a fake border checkpoint in the lobby and demanding to see classmates’ “papers” as a mariachi band played.

The tone-deaf stunt at the $65,900-a-year all-boys Upper West Side prep school lit up a Facebook group of local moms at first puzzled by the musicians playing outside while surrounded by teens waving American flags — with some of the mothers thinking it was a May Day or pre-Cinco de Mayo celebration.

A thread on the “UWS Mommas” Facebook group viewed by The Post revealed the parents’ growing chagrin as they learned more details about the scene.

“It was senior prank day,” a parent wrote. “The seniors decided to set up a border patrol and made all the students go through it at arrival. I can’t imagine how humiliating it felt for the Latino students.”

A senior prank at Manhattan’s elite College School featured a fake border checkpoint and a mariachi band. Luiz C. Ribeiro for New York Post

Another mom, alluding to President Trump’s border and immigration policies, added to the thread: “If that’s a prank, it’s in serious poor taste at the moment, and needs following up.”

Additional shocking details about the stunt were revealed by Gothamist, which first reported on the boys’ antics — and subsequent outrage from school staff and other students about the alleged anti-immigrant motives.

The pranksters set up a cardboard booth May 1 wreathed in caution tape, from which they asked to see students’ “papers,” Gothamist reported.

They also had an inflatable eagle riding a motorcycle in the school’s lobby and adorned its entrance with American and Texas flags, according to the report.

The mariachi band played outside while other students waved American flags.

“It was really bizarre seeing middle aged Latino men playing music next to white kids draped in the American flag. It looked exploitative,” a mom on the Facebook forum wrote.

Leadership at Collegiate School did not return Post requests for comment. Gothamist said the head of the school, Bodie Brizendine, emailed parents and staff that officials “regret that this ‘prank’ took the turn that it did.”

Smirking students leaving class Tuesday all denied knowing about the prank to The Post. Luiz C. Ribeiro for New York Post

A teacher outside the school Tuesday confirmed that an embarrassing jest went awry but didn’t know specifics.

“They brought it up in our meeting but they didn’t go into detail,” the teacher said. “They were just saying how it was unacceptable.

“Now, I’m even more curious as to what actually occurred.”

Scores of smirking students left class Tuesday and denied knowing what happened to The Post.

Collegiate School’s many illustrious alumni include John F. Kennedy Jr., “X-Files” actor David Duchovny and former New York Times publisher Arthur Ochs Sulzberger Jr.

Its current board of trustees includes NYPD Commissioner Jessica Tisch.

The centuries-old school last year was embroiled in controversy after its former head, David Lourie, allegedly ripped an antisemitism task force as a “joke” and a “power play by Jewish families” to have him ousted.

Lourie resigned, and Brizendine took over.