I wrote about building design yesterday....corridors that could be locked down...isolating or trapping the bad guy. Video cameras in the halls.
My grammar school was two floors but all the first floor classrooms had exit doors.
These lockdowns "trap" the children. We need to approach a solution as if it were a fire.
The attacker at Virginia Tech (also a school) was a student ~ an insider. He was able to trap his victims inside the building with a chain. That also locked out the cops AND combined with chickenwire glass, made sure they couldn't get in.
What was needed was a second student with a firearm!