My son goes to (and other graduated from) a high school with well over 3k students. It is the size of a small college campus with four large classroom buildings and a separate gym, so between classes there are always hundreds of students walking outside. The local police do patrols, but everyone acknowledges that if a shooter is determined enough, there’s little they can do. He’s graduating next week. Day to day, I don’t think about it too much, but whenever there’s another mass shooting, I get terrified.