Treat like a fire.

“Come with me to the library at Columbine High School,” Grossman said. “The teacher in the library at Columbine High School spent her professional lifetime preparing for a fire, and we can all agree if there had been a fire in that library, that teacher would have instinctively, reflexively known what to do.

“But the thing most likely to kill her kids — the thing hundreds of times more likely to kill her kids, the teacher didn’t have a clue what to do. She should have put those kids in the librarian’s office but she didn’t know that. So she did the worst thing possible — she tried to secure her kids in an un-securable location. She told the kids to hide in the library — a library that has plate glass windows for walls. It’s an aquarium, it’s a fish bowl. She told the kids to hide in a fishbowl. What did those killers see? They saw targets. They saw fish in a fish bowl.”

Grossman said that if the school administrators at Columbine had spent a fraction of the money they’d spent preparing for fire doing lockdown drills and talking with local law enforcers about the violent dangers they face, the outcome that day may have been different.

via Police One.

This is taken from the middle of an excellent article.  It starts with the historical problem and walks you through a simple solution.

Common sense for everyone, and every school.