Aside from the issue of gun control, safety in schools is of paramount concern.
Why not consider the use of highly trained K-9's firstly as a deterent against guns & drugs, secondly as means of neutralising an active shooter or threat. They've been used for centuries as guard/protection dogs and we all know how far they come over time. They are one of the few, if not, only animals that can read our eyes and the intent behind them.
Obviously you would choose the right dogs (numbers depend on size) for the role as you'd require a confident, social, intelligent animal that is capable of moving through varying envionments with kids, adults, other dogs/animals while being able to identify/analyze/neutralise any possible threat. They can also sniff out weapons in bags or hidden in the buildings or on the grounds. Soldiers trust them with their lives in combat, maybe a nice way to retire military working dogs - Great hours 9-3, good holidays & lots of pats from the kids!
But don't mess with them;
[video=youtube;yadeRfqjMMM]http://www.youtube.com/watch?v=yadeRfqjMMM&feature=youtu.be[/video]