Lots has been hashed out here, and reading the comments they just keep circling back around. Working in schools for 20 years now, I can make a few points.
We know that in any mass shooting, when the shooter is met with armed resistance they are, at the very least slowed down. There is no doubt about. We also know that the sooner armed resistance is met the lower the number of causalities. With Columbine we saw just how time is the most important factor to saving lives. Prior to Columbine it was pretty standard in such cases to set a perimeter, then work your way in room by room and spot by spot. This means that at columbine there were officers sitting outside waiting for the go ahead to enter while the gun man were still shooting. Now with our local officers our response plans are once there are 3 officers, they enter and go directly to the shots. There is no methodical clearing of rooms, they engage and stop the target ASAP. Knowing again that time lost equals lives lost. What does this response say about having armed resistance at schools? More than the single resource officer or an easy to identify security officer?
In my 20 years I have worked in a 1/2 dozen schools. In every single school I have worked there have been other teachers I would gladly trust with my life and with a firearm. It is sad that many have such low opinions of teachers and that as a whole our society does not honor teachers and the teaching profession. Often time when I mention concealed carry for teachers and staff, I get hammered not because of actual facts, but by perceptions. I ask his simple question... What is your perception of a teacher? What does a teacher look like/act/etc.? This perception is hard to overcome. As a teacher I stand 6' 2" weigh 280 pounds. I can lift a a Chevy 350 block with ease. In my school I also have a very good friend, the librarian, she is petite, soft spoken, very unassuming... In the fall we get together every week and share stories of hunting and shooting etc. In my school we also have 2 combat vets, etc. My principal grew up working the family outfitting business, etc. My point is simple, our schools are filled with all sorts of people with all sorts of backgrounds. As a teacher, I would love the opportunity to concealed carry. I would also have no issues if other in my school were also afforded the same ability. Do I feel it would change any dynamics of the student teacher interactions? Not likely, other than you would not see nearly as many videos where some thug decides to attack a teacher.
As a teacher and concealed carry permit holder, I am afforded the ability to carry through out my community. I can carry at the store, mall, movie theater, gas station, etc. I can carry at the park... I have taken the test training etc. I have met a minimum requirement for society to say that I am safe to carry. I carry for the safety of my self and for others. However when I am responsible for our kids, when I am the adult supervising 20+ student in my class or when I am in charge of lunch duty and watching 200 students eat, I am not allowed the same level of defense and protection.
I am not arguing that every teacher needs to carry, heck I am well aware that would be silly. But I also believe that our schools could benefit from having armed unidentified resistance. As it stands right now, despite having training, despite having the ability to potentially prevent such an act. My training forces me, school policy says, that should the worse case happen, I lock myself in my room, turn the lights off and hope when the door it opened it is the police and not the gunman.
I truly feel that even the possibility of meeting a concealed carrier is a deterrent to the crime. Also if the shooter engages an armed teacher or staff they now no longer have an uninterrupted access to targets. If the Cc breaks the cycles for even a few seconds we know that time is again lives.
There are many examples where a CC has stopped such rampages. In Texas at a movie theater, Colorado Springs Church, Seattle Shopping Mall...
So what I have done is presented the response... How can limit and prevent carnage as it happens, this approach might prevent some acts, but will not work over all and it is simply about limiting the damage when it occurs.
So that leaves us with the simple question of prevention... OK not simple at all...