CNN has an article on various products to protect our school children
I actually support such developments, and believe that the mere positioning of book shelves, bullet resistent whiteboards, and steel rebar door locks (hole in floor, drop bar in, door cannot be opened). Could do a lot to make our classrooms safer by providing areas which can shield students.
If one can keep a shooter out of the classroom, and provide a barrier for the students to hide behind. They should be safe until authorities can arrive and subdue the shooter.
Sadly, I think very little thinking of this sort has been implemented at any school boards across America.