I'm saying that if the only requirement a teacher needs to carry a gun in a classroom is a concealed weapon permit, then that standard is too low. If you want to arm a teacher, you're going to have to develop a training course that's a bit more complicated than a 4-5 hour class with no exam.
The school resource officer at Columbine was dealing with two heavily armed men. As far as he was concerned, there could've been more, and he didn't know the school was mined with hidden bombs. Everybody was a threat. Children were running everywhere - just watch the video tapes.
Harris and Klebold started firing at 11:19, the school resource officer returned fire at 11:28, and other deputies arrived on scene around 11:30. Trained SWAT teams didn't clear the buildings until an hour later, and these are professionals trained in urban warfare. Do you really think that a handful of teachers, with nothing more than a 4-5 hour class in firearm safety, carrying concealed handguns would've saved the day?
My ideals have the goal of saving lives, not adding to the casualty list. The last thing I want is to see sons and daughters dropping dead in the cafeteria because they made the mistake of running in a blind panic through friendly fire.
edit: I tell you what, you show me data where armed teachers would've prevented school shootings and I'll support your position.