Here’s something I noticed on my first morning as a teacher at an extremely rough and low performing high school in Brooklyn. Every kid (and they were all black) in the school had to walk through metal detectors on the way into the building. I got to bypass the security and walk right in, even though I had no track record, and no one in the school had ever seen me before. That policy sent a bad message to the students. Even those who were good students and played by the rules were treated as suspects. From that day on, I tried to go through the metal detectors anytime my students had to. I’ve been thinking a lot about those days since reading about Philadelphia’s John Paul Jones Middle School. As Jeff Deeney explains in The Atlantic: “During renovations, they removed the metal detectors and barred windows. The police predicted chaos. But instead, new numbers seem to show that in a single year, the number of serious incidents fell by 90%.”