Time to stick my oar in the water. NDD (& allies) - I hate to pile on (not really, stationary targets are easier to hit

) but I think you're letting the current "it's for the children" vogue affect your normally impeccable judgement. Hundreds of thousands of lawful citizens carry concealed every day - without incident, wherever it's allowed. Violent crime statistics in areas with concealed carry statutes are decreasing, precisely because the criminals don't know who might shoot them. Unfortunately - in my personal opinion, federal and local laws make school zones (and the surrounding areas) perfect hunting grounds for deranged individuals seeking defenseless prey. Standard target rich environment with extremely low risk and a very high probability of success. I (and apparently a few others here) think that should change. That's why I asked the earlier rhetorical question about terrorist violence in Israeli schools. The answer is - not nearly what anybody would expect given the violence/unrest in the region. I'll have to Google the incident to get more details but I'll bet the death toll was mitigated by an active, armed defense of the students.
Lecture Mode (All that risk analysis, threat management, statistics & probabilities, and simple economics training really is handy sometimes.) The gunman in the Pennsylvania shooting picked his victims precisely because they were perfect victims - incapable of resisting. Predators do that. Current risk analysis clearly shows that the US threat is still "crazies". That usually means one or two gunmen with a lunatic/apocalyptic adgenda. Criminals don't target schools - no profit motive, and crusaders (on the order of Beslan) haven't gotten here yet. God help us when that happens. Until it does, let's concentrate on the most realistic threat - and the most cost effective method to do something/anything to address it. That threat is the deranged gunman/gunmen, usually 1-3 in number. The more lunatics involved, the more likely it is to be discovered and disrupted by law enforcement during the planning stages so more gunmen is an unlikely scenario.
The quickest, cheapest way to address the threat is to allow responsible citizens to carry weapons on school grounds. (NOTE: I did not say competent or qualified. By the time acceptable definitions of those two terms got out of committee we would already be facing multiple Beslans right here at home.) The current CCW programs already establish a legally defensible method of determining responsible. No it is not a perfect system. Nothing manmade is. It does serve society's perceived needs. I like TR's suggestion of sending volunteers to "summer school" but I don't want to make it the requirement because then - again - nothing would get done while the experts argued curriculum. Besides, heretical as this may sound - we all know performance in training is not always an accurate predictor of performance in combat. Our hypothetical armed teacher is not expected to conduct CQB against the 3rd Chechen Horde.
Let's try some role reversal. Take away your professional training, personal experience, teammates with similar qualifications, explosive breaching, distraction devices, body armor, etc. - in other words reduce yourself to the level of the historical "school shooter" model. Now tell me you would be comfortable busting through a classroom door against a known armed threat (in an unknown location) probably shooting from a kneeling supported position in "desk defilade". We are all familiar with what happens to the "target" in the fatal funnel when the defender can fire from cover. Personally, I would move on to an easier target. In today's classrooms that's 25+ lives potentially saved. I ascribe to Robert Heinlein's philosophy: "An armed society is a polite society." I also think it's a safer society too. Just look at the crime stats for Dodge City during the heyday of the cattle drives.
Is allowing responsible citizens (not just teachers, staff, and SROs) to carry on school grounds a perfect solution? No. Does a perfect solution exist? I don't think so. Is it better that what we have now? I think so. Does the issue merit discussion? Certainly. At least the liveliness of our discussion says most of us are passionate about the issue one way or the other. Personally, I think the children would probably be safer in a locked-down classroom with an armed teacher than they are every day in the average mall parking lot.

Peregrino