I've seen this idea posted and each time it completely fails to ignore a couple of key facts.
1. The people who do this are crazy. To assume they'd be deterred by rational thought of potential harm to themselves while committing the act is pretty much saying that they aren't crazy and are capable of rational thought. They're nuts, out of touch, lack reasoning......whatever. That's why they do this stuff.
So the staff members would have guns, then what? How does that change this situation when a guy goes into the classroom? If he shoots the adult in the room first the gun is either on the floor or in the desk and there we are back to step one of being unarmed. Not to mention, where are teachers going to store these guns so they are both 100% inaccessible to students AT ALL TIMES yet also readily accessible to the teachers in a split second AT ALL TIMES? Are teachers going to be given holsters to pack around in elementary schools?
2. Arming staff assumes that the nut won't simply up the ante. Provided they even care that people are armed........most kill themselves, or at the very least prepare to be harmed themselves. You don't wear vests and military masks if you aren't expecting someone to return fire. The possibility of being shot is there as it is and it doesn't really deter one bit. Instead, they simply armor up so they can do the most damage possible before getting taken down.
Or maybe instead of guns they move onto other things like a truck with 50 gallon barrels of gasoline in the back. Drive one of those into the cafeteria at lunch? Guns aren't stopping that. Or hell, what if it doesn't even have gas and the just drives through the schoolyard at recess and runs over a bunch of kids?
These people don't care if there are guns around. They're hellbent on killing people. Pinning your hopes on guns being a deterrent is misguided because there are nuts out there who just do not care.
But lets pretend for a minute that it would deter people.
Since 1980 there have been 137 school shootings. Most have few losses of life. The three biggest have been Columbine, Sandy Hook and Virginia Tech.
Those 3 have accounted for 72 of the 297 deaths that have occurred in those shootings.
Scaling it back to the beginning of the year that Columbine happened as it was basically the first time we saw true evil and intent, it looks as though there have been 69 school shootings. It's kind of hard to count them up on that timeline. Also looks like 184 deaths.
3 of 69 shootings accounting for 72 of 184 deaths. These are the ones where the nuts don't care. So even if we take just these 3 and credit teaches who carry guns with being able to prevent the other 66, there are still 72 deaths. If teachers carrying guns can effectively reduce 95% of all shootings but the net effect is a 60% reduction in death, is that good enough? I don't think so.
I haven't looked it up either but I would bet a number of the incidents are simply some kid taking a gun to school because he thinks he's a hard *** and after things escalate to a certain extent, he shoots someone. Or maybe he went with the intent of shooting a specific kid and that was it. Those types of things happen before anyone even knows they happen. Teachers having guns may or may not stop those. What they might result in is the shooter getting shot, which would be the best case scenario compared to teachers opening fire and accidentally hitting other students.
Teachers carrying isn't the answer because there are people who don't care. They'll either go in anyway or step their game up. It's gonna take a number of different approaches. Like all things, there is no single answer. Since when has a problem like this ever been solved by the simple answer of arming teachers?
The real tragedies are premeditated and planned. The attackers have the element of surprise. They have the upper hand in every possible way, especially if they are bringing in multiple weapons and can put out more rounds than a teacher could.
And another question, what is the course of action for a teacher? They hear gunfire and leave the room, telling the kids to lock the door behind them? Now you have a room full of kids, no teacher present to direct them and no guarantee of stopping the shooter? How do you coordinate an evacuation of that classroom without an adult present? Class full of 5 and 6 six year old kids, nobody there to direct them and basically no way of communicating efficiently with them to provide directions?