Our school also has MANY doors to the outside. They dealt with this by putting up an 8-foot chain link perimeter fence. Most doors are also now locked during the school day.

At my child's preschool, which was also a private school, they put codes on all the doors.

There is also a police officer assigned to every school in my district now. YES. EVERY SCHOOL. I don't know if they are always there, but it seems like it. I shudder at the cost. I live in a mid-sized city without any notable history of shootings, gangs or school violence.