High school senior Lucas Gilmour was sitting at his desk during first period last Thursday morning when Principal Paul Belzer’s voice was piped in over the P.A. system.

“Our school was vandalized with anti-Semitic, homophobic and racist content last night,” Gilmour recalled Belzer saying. “Maintenance has already covered it up, and we will have it painted by later today.”

Gilmour immediately hid his face in his hands. As the student body president, it had been his goal this year to embrace diversity at Burlingame High, he told J., and he had been working with Belzer on doing just that.

“It was a big blow,” he said.

The morning announcement on Sept. 5 came just hours after maintenance workers at Burlingame High School arrived on campus to find multiple instances — “ten to fifteen distinct sites,” the student newspaper Burlingame B reported — of bigoted and hateful graffiti drawn in black spray-paint outside the school. A photo published in the school paper shows a worker scrubbing a swastika off of a red-and-black school banner bearing the Burlingame mascot, a panther.

Burlingame Police Department Lt. Laura Terada described the graffiti as “all over the board”; the content included anti-gay, racist and anti-Semitic words and symbols. She said police did not know whether it was the work of one or several people, but that officers had “multiple leads.” No suspects had been identified as of Sept. 10.

As officials continued to investigate the incident, which Terada said could be prosecuted as a hate crime, students responded in their own way. On Tuesday, hundreds of them wore red T-shirts or hoodies — the school color — in a display of “unity against hate.”

At lunchtime, they congregated in a sunny, breezy courtyard of the school — where outdoor scenes from the movie “Dangerous Minds” were filmed. Students plopped their hands in paint before stamping them on banners bearing messages like “We are stronger than hate” and “Panther strong.”

The words soon were completely covered by students’ five-fingered marks, stretching from end to end on the banners, which would go on to hang in heavily trafficked hallways. Bob Marley’s “One Love” and other music bumped over loudspeakers.

“It was a good vibe,” said teacher Nicole Carter, who heads a course in leadership. It was her students who planned the unity event.

“This is our way of being able to make a statement together,” she said, without everyone having to write out individual messages. “It’s their way of saying, we’re all in.”

Burlingame schools have battled similar problems before. In fact, last week’s incident wasn’t even the first this year involving anti-Semitic and anti-gay vandalism at the high school. In April, a Jewish student’s locker was broken into and defaced with a swastika and the word “fag,” written in deodorant. The perpetrator was never caught, the student’s mother told J.

In another incident, Julie Ellman said her son was insulted with anti-Semitic taunts during the 2017-2018 school year at Burlingame Intermediate School. And in January 2016, the Anti-Defamation League received a report of a swastika drawn on the back of a Jewish student’s chair in a Burlingame school.

It’s a strange and unsettling pattern that reached an apogee last week at Burlingame High — an academically strong public high school that boasts among its alumni Salesforce founder Marc Benioff. The sprawling campus, located in the Peninsula town where the average home price is $2.1 million, has a student population of 1,425.

Belzer said his administration was taking the incident seriously and developing a response. He appreciated the way students in Carter’s leadership class took a “proactive” step in denouncing the hate speech.

“We ultimately want to take responsibility for our school and for our school community, the school culture that we create,” the principal said in an interview with J. “One one hand, you respond to the events that happen. And then you figure out how to move forward.”

Belzer does not think the graffiti, which the school district is investigating with the police department, reflects the dominant culture at Burlingame High School. Neither does Gilmour.

“We know that our school is not that,” he said about the markings. He said he was moved to tears by the overwhelming show of support by his classmates in the intervening days. “Our school is not this hate crime, that’s not what defines us,” he said.

“Look how many people are wearing red just around here,” said Heather Lee, student body vice president, pointing to the throngs of students around her.

Lee and Gilmour, close friends since elementary school, both wondered whether today’s political climate is playing a role in student behavior. According to the ADL, anti-Semitic incidents nationwide more than doubled between 2015 and 2017, to 1,986, the most in decades. California sees some of the highest numbers of anti-Semitic harassment, vandalism and assault.

“It trickles down,” said Lee. “ A lot of what high school is, is trying to fit into a certain status quo.”

“By people normalizing hate speech, other high schoolers think, ‘I’m just saying it as a joke.’ But that normalizes it for a lot of people,” she said. “And then they start to think it’s OK.”