Most school shooters are using AR type rifles. A 9mm is no match for that. If shooters know that a teacher might have a concealed gun, guess who gets shot first..
How would the shooter know which teacher had a "concealed" gun? I have no doubt that if I was a teacher that was armed with a drawn 9mm pistol and you came around a corner I could shoot you before you could raise your AR-15 and point it at me.
