The idea of non-resistance to aggression seems to have come from some of the eastern religions and worked OK for Gandhi, but he was up against a mostly moral, rational, and ethical opponent.
Hunh? Are you sure about this? Using non-violent civil disobedience to resist an imperialist power is something entirely different from personal self-defense. Try to rob some people at a Hindu temple, and you'll be fed a lot of knuckle sandwiches. My guess is that the "play dead" directive has something to do with American legal culture. The school doesn't want to get sued if the students get hurt trying to do something that the school has trained them to do, like climbing out the window to get away. I seriously doubt anybody in the American education system cares or knows anything about Eastern religion. I'm just guessing, but perhaps someone involved in training for active shooter scenario can tell us...
I think a lot of people will protest your characterization of the largest empire that the world has ever seen as "moral, rational, and ethical." Alright, perhaps rational for the most part. But you don't get to be the biggest empire without spilling tons of innocent blood. This forum is probably not the right place to discuss history, though.