In a school attack, distance and timing are everything. From where would a shotgun necessary to fire beanbag rounds come? The only effective way to employ firearms is for staff to carry them, concealed and secure, on their persons. A shotgun locked in a safe in the principal’s office suite is of no use if the principal with the key is at home sick, at a meeting at administrative offices, or wounded or dead in a hallway. Even if they could get to that shotgun, the time involved will cost lives, and no beanbag round can be relied upon to stop a killer, even if one could get close enough to fire it before being cut down. The same applies even more to a Taser, which is even more range-limited, and the barbs of which may not penetrate heavy clothing. Consider too the tactical horror of having to confront, with less than lethal means, multiple killers whose weapons have much greater effectiveness and range.
Any rational person must do all they can to avoid ever having to use deadly force. But when it becomes necessary, they must employ it immediately, accurately, surely, and decisively. “Shooting to wound,” firing warning shots, and shooting people with rubber bullets or beanbags are all legally unnecessary and truly dangerous. If one has the legal grounds to shoot, they must do it with sufficient accuracy and with a volume of fire sufficient to immediately stop the attack.
One never shoots to kill; one shoots to stop. If, as a consequence of being stopped, the attacker dies, bad for him, good for the children, school staff, and society.
Less lethal methods for civilians are uniquely and unreasonably dangerous. Not only are they highly unlikely to stop a determined attacker, they are an inexcusable waste of time in situations where every second means lost lives. If they don’t immediately stop an attack, the teacher employing them will be most unlikely to survive to try something more effective.
The only rational response to active shooters, the only response that will deter attacks and can immediately end them, is to train with and use appropriate firearms and ammunition. Beanbag rounds and similar technologies are appropriate only for highly specific tactical situations encountered by the police, backed by firearms. The fact that no rational police officer would assault an active school shooter with less than lethal technologies speaks volumes.