Eric Eisenstadt doesn’t consider himself a flame-thrower. A physics and biology teacher at Manhattan Hunter Science High School, he says teachers shouldn’t “proselytize their own views” in the classroom. But he doesn’t think bias belongs in the classroom either — and after the presidential election, he wanted to make sure his students knew that.

So, on Monday, Nov. 14, nearly a week after Donald Trump’s upset victory, he posted a sign to his door proclaiming his affection for his students. All of his students.

“I love my Muslim students. I love my black students. I love my Hispanic students. I love my gay students. I love my disabled students. I love my poor students. I love all of my students and I will fight for you, not matter what,” he wrote in multi-colored marker. “And if he, or anyone else builds that wall, or any wall between us, I will teach my students how to tear it down.”

The sign didn’t get noticed much at first, he said, but then a friend posted a photo of it on Twitter and it attracted more attention, both inside and outside the school. Other teachers across the country have posted similar messages of love and encouragement, but Eisenstadt’s had a particularly wide reach. The photo has now been liked or retweeted nearly 7,000 times and a related Facebook post has garnered dozens of approving comments.

Chalkbeat contacted Eisenstadt to learn more about his message.

“I don’t think you can learn if you’re concerned about greater issues happening outside, if your whole safety and security are in jeopardy,” Eisenstadt explained. “I just wanted my students to feel that at least the school is a place where, regardless of what’s going on outside, racism will not be tolerated.”

While Eisenstadt was careful to write that he loved all of his students, he worried that some — his white or Chinese students, for example — might feel left out. He explained that he named certain groups on the sign because they’d been singled out during the campaign. “I wanted to make it clear,” he said. “I think they got it.”

So did his fellow teachers and principal, he said. “Once this became a viral thing, the principal came by and he said he thought that was a great message,” he said. “It was all positive. Very positive.”

Obviously, not everyone agrees. “Time for him to be expelled,” wrote one online commenter after a story on Eisenstadt ran in the Daily Mail. “If he loves his students, he should stick to teaching them,” wrote another.

Eisenstadt seems to understand their concerns. “This is not something I would normally do,” he said. “I scrupulously avoid telling students who I am voting for.”

This year, he said, he made it clear to them that he harbored no ill will toward those with different views. “I explicitly told my students, ‘I have no problem if you like Donald Trump or if your parents like Donald Trump,” he said. “I have no problem with you.”

Eisenstadt knows his sign is controversial, but says it’s also an important statement in a school with a large number of Muslim, Hispanic and black students.

“I can easily picture if I had done this in another school, I could have been told to take it down,” he said. “I’m grateful, frankly, that people understand what I’m trying to do.”