And if the student was not wearing the backpack when the person started shooting?
Or what if the shooter aims for a part of the body not covered by the backpack?
I think the theory is that the students would crouch down and use the backpacks as shields.
The real purpose, of course, is for the businesses that market the backpacks to profit from parents who buy them as a useless gesture, so that they can pretend they’re protecting their children.