BOSTON — Every morning, I stand behind the metal detectors, searching bags as students enter the school. They come clutching iced coffee and bags of chips, their faces burned by the wind. Sometimes they raise a hand in greeting, but mostly they look off into the distance, bobbing their heads to the music in their earbuds. I am an administrator at a public high school in Boston, serving almost entirely low-income black and Latino students, and that means every morning I am the white guy at the metal detector telling them they are suspected of a crime as they walk into their school.

I’ve been an educator in urban schools for over a decade. There are mornings when I imagine a different life, one where I take the train downtown and sit at a desk, actually sit, for 15 minutes over the course of a day. But it is just a passing thought. I keep on going to school because I believe in the work, which is another way of saying I believe in the kids. And then I arrive, and I see their faces framed by metal detectors.

There are metal detectors at the entrance of nearly every public high school in Boston — I imagine it’s the same in most major cities. Last year, when I started working at this school as part of a new administration, we were determined not to use them. We made it until October, when a student brought a knife to school. He was a gentle kid, a ninth grader, and he said he’d brought the knife only because some guys in his neighborhood were harassing him on the way to school and he needed to protect himself. But our first job is to keep the school safe, and so we asked the district for metal detectors, which arrived before 7 the next morning. I had never seen anything arrive so promptly from the district. Textbook orders take months.