"Bear Pepper Spray" is available between $30-$40 dollars a can. It sprays a cloud of Pepper Spray from 10-30 feet away and could potentially disarm someone without having to get up close. An attacker is effected by inhaling or getting it in their eyes incapacitating them allowing teachers and students to escape.
If an armed assailant were to enter a classroom, or break into a classroom which was on lock down, someone with little training would have a way to defend themselves that was non-lethal. If a child were to get a hold of it, it is non-lethal. It would give those in the situation an opportunity to escape.
This is an inexpensive and non-lethal way to give teachers the and students an opportunity to escape. This could also be implemented safely and quickly with minimal cost.