Let's see... Defend against a guy breaking into my classroom.
I have a choice... Baseball bat or NOTHING.
I think I'll choose the bat.
I don't think anyone believes that is an ideal solution, but anything that gives you even a little edge is better than just sitting there with your eyes closed waiting for the bullet. A shooter has to come through the door to get into the classroom. When he is in that funnel, he is actually quite vulnerable. Something like a bat or a baton may not help the people where he initially opens fire, but if he goes from room to room, it might make a big difference.
Again, not an ideal solution, but better than nothing.