Several US schools to install pepper-spraying drones to respond to school shootings
(www.theguardian.com)
Also, let me point out that flying a drone at an armed person is an excellent method of getting them to shoot at it. And while drones are rather hard to hit, schools tend to be full of kids who are much easier to hit.
Also, who is going to operate this? And train on it? It's not easy to do this, so I'm assuming it'll be untrained morons fucking things up as usual.