My idea is along the lines of the Armed Cockpit Program. It would be voluntary, and require specialized training, background check (something teacher's aren't even subjected to now), and psych eval. And be resrticted to and ENFORCED as CONCEALED carry to eliminate potential trouble-makers knowing which teachers are armed. It is the not knowing that stops these attacks before they occur. Posting a guard is only putting a bull'seye on the guard and doesn't provide defense in-depth.