A black teacher at Manhattan’s Beacon High School told cheering students to boycott the elite campus Monday after an incident involving a white Jewish girl sparked complaints about a racist environment.

“What we’re asking of all students: Do not come to school that day to show solidarity for the support of not just students of color but all students at Beacon in providing a safe space,” said a teacher who identified himself as “Mr. Green” at Friday’s boisterous cafeteria gathering, which was videotaped.

“Until the demands are met, students are not to return to school,” the teacher — identified as science instructor Demetrius Green — exhorted the crowd of hundreds of teens.

Some Beacon students called for a sit-in instead, suggesting kids wear black and tape their faces.

But the teacher asked, “What is that going to do? Students before you, before I, have done the same thing, and nothing has happened.”

On Dec. 2, about 300 students walked out of the high-performing Hell’s Kitchen school for 40 minutes to protest admission criteria they say limit integration.

The student body is 47 percent white, 20 percent Hispanic, 14 percent black, 9 percent Asian and 10 percent “other.”

Friday’s protest was set off by allegedly “racist remarks” that a black student claimed he overheard a white Jewish girl make in a confidential meeting Tuesday with two white Jewish guidance counselors.

The girl told The Post that she was only seeking support for her own college plan at the time. Disappointed that she was put on a waitlist at a top university, she and the counselors were reviewing Scattergrams, charts on admission data, showing that some students with less academic qualifications than she were accepted, said the teen, whose name The Post is withholding. The counselors mentioned scholarship programs for minorities such as Posse and QuestBridge, she said.

“The context of my private conversation included my disapproval about the unfairness of students who were accepted to college without meeting the rigorous criteria that I and others worked so hard to achieve, because they might be athletes, afforded financial scholarships, and/or get seats based on affirmative action programs, as opposed to academic achievement as the first and only criteria,” the girl explained in a statement.

The black student barged into the meeting and berated the girl and her counselors, causing a commotion.

As word spread, the girl became the target of cyberbullying and threats, she said.

One Instagram post accused her of saying “minorities stole her spot,” and “Im not gonna go to schools for black and brown people or ppl who are retarded.” It concludes, “…she’s definitely Messing with wrong group of ppl. She CLEARLY don’t know how we grew up cuz that bitch looking to be destroyed LITERALLY.”

Another Instagram post said, “As a proud future QuestBridge scholar, let me tell you something about myself: I deserve it. If you got rejected from a school you wanted to attend, do not bash other people who have worked hard their entire lives and were not born with silver spoons in their mouths.”

The girl said other students twisted her words out of context and falsely accused her of racism.

Later, she said, one of her teachers chided her, telling her, ”People are going to hate you because you’re Jewish,” and “You don’t understand your privilege.”

The city Department of Education, United Federation of Teachers and the Special Commissioner of Investigation for city schools received written and verbal complaints about Green’s call for a boycott.

The teacher is accused of inflaming racial tensions, encouraging kids to be insubordinate and violating DOE attendance and safety regulations.

One student who spoke in the cafeteria Friday blasted the school’s white administrators and teachers for a “lack of initiative” against what he described as a hostile environment for kids of color.

“This isn’t the first incident at Beacon that has involved racist rhetoric,” he said, citing classroom discussions on slavery and use of the N-word.

“We have a college office of counselors that look nothing like the student body” and who tell black students, for instance, “to limit themselves by only applying to state schools,’’ the teen said.

He also complained that the administration had failed to apologize for the white girl’s remarks.

“Here we are three days later, and kids of color have not received an acknowledgment about the situation,” he said.

On Sunday, some students posted a list of “Official Demands,” including a call for Beacon to publicly apologize for “allowing racism to fester” for years; ”probes of the guidance counselors” who met with the white girl; mandated workshops on “implicit bias” for students and staff; and ensuring that faculty hiring “mirrors the diversity” of NYC’s students.

It also demands that students who take part in the boycott or sit-in “will not face any repercussions.”

Beacon principal Ruth Lacey emailed students Sunday evening saying she was “moved by the passion’’ of the cafeteria speakers, according to a copy obtained by The Post.

“I understand that some students will be continuing to demonstrate the seriousness of these issues throughout Monday,” she wrote, inviting kids to a discussion after school Tuesday.

Asked by The Post about Green’s conduct, Lacey referred questions to the DOE’s press office.

The DOE said it will investigate the “reports of bullying and staff misconduct,” including allegations against Green.

“Students and staff at Beacon deserve a safe, supportive and inclusive school,” said spokeswoman Miranda Barbot. “We will support the school community’s efforts to foster a welcoming learning environment for everyone.”