Is it realistic to believe that a teacher could effectively defend against an active shooter, using an AR-15, armed with only a handgun?

Tired of seeing mental health, gun control, etc as the blame for the increased violence. Guns have almost always been a part of American culture. So what has changed from today to, let's say, 40 years ago? One answer. Us.
Our society, our families, our beliefs, our morality, our etc. Etc. We have changed. We are to blame. Stop throwing a false narrative or diagnosis on it.
We are the problem and always will be. The problem has just gotten worse.

I would like to believe that I would give it a try, it is better than doing nothing. And if I can save a few children in the process, so be it...

I believe I could, with my minimal training. I make no claim to being a bad-ass. Zip zero zilch. But I am fairly certain I would engage in this instance, and protect my kids. If I can, why couldn't a teacher with training? But ok, say you're right, arming teachers is not the best course. Fine. Arm vets. Stick them in schools to walk the halls. 5 of them in a school like that would give pretty good coverage, and wouldn't strain anyone's budget.

I have the privilege to live in a school district that has had armed staff members for the past four years. There are prominent signs posted at the entrances to the school grounds and at building entrances announcing that fact to one and all. My grandurchin has been a student there for three years. I attend school functions such as six week awards ceremonies, programs, lunch visits and vet visits regularly. We've had a number of sleepovers and parties here for her and her BFF's(Cows and horses and dogs, oh my!) The point is that I know the staff at the school and I know a lot of the kids at the school. I've never seen any evidence of guns in the school. No armed teachers prowling the halls. No suspicious bulges on the ankle, at the waist, in the armpit or any place else on any of the staff. And as for the traumatic impact of guns in school on the kids there, there's no evidence of that either. I've never heard a student mention that her teacher or the vice principal or the maintenance guy had a gun. Kids are not stupid or unaware; if guns were upsetting them they would know who had one, where it was and who had what kind of weapon. And they'd talk about it. They talk about everything. I've never heard a word about guns at school. From staff or students.

The policy of arming school staff here has had none of the negative effects the talking heads have been postulating. In actuality the policy has contributed to a happy, secure and effective school system.

Wouldn't surprise me any that those great big red and white signs announcing the policy may be the most effective part of the policy.

The concept is that by arming teachers, or having visible security, you are creating a deterrent.
The deterrent hypothesis has some merit, I mean when is the last time someone tried to assault a gun show?

Regardless of where one stands on guns in general, one thing needs to be clearly understood: Guns are not going to go away.

Setting aside the legal, historical and cultural aspects, one is left to contend with the simple truth that guns exist and will forever be present. Americans in general don't like being told what to do, and the passion of much of the gun owning American public leads me to believe that--if only on principle--many will simply never give them up. And the harder its pushed, the harder they'll push back.

There's no magic magnate that will suck up all guns in the US; and military or government officials scouring the countryside , kicking in doors to every household in the country looking for guns will never happen (and frankly would be a bloodbath if it did). Too many people are basing their opinions regarding what "should" be done on what they wish could be done, not based on the reality "on the ground". The reality is there's hundreds of millions of guns, and no amount of wishing will get them all or even most. Its time to deal with things as they are, even if you hate guns to the core of your being.

While one can find isolated incidents throughout history, mass shootings on the scale we have had in the last, oh say 25 years, was not really a thing in the workplace or schools. For those of you NOT of an age to have lived prior to this period of high-profile mass murder, you might not be able to understand that there was a time when no one worried about going to work and having a disgruntled employee blast away at everyone or that the picked-on kid will come to school to kill as many as he feels needs to feel his pain. You certainly will find it unimaginable that gun safety was ubiquitous in American schools then and that in many, generally rural, parts of the country it raised NO eyebrows when kids would bring their firearms to school to go hunting before or after class.

The guns have always been there. All kinds of guns. For every weapon an American Grunt carried into the field, there was a civilian counterpart. Something has changed in society; I'll let y'all fight over what that "something" is. But that's the reality. So in conclusion, if one wants to find solutions, start by accepting the reality.

I'd bet money the teachers who died shielding the children would have stepped up. Considering four trained officers didn't engage the enemy during an active shooter situation, what is the worst thing to happen? There is no perfect answer, but, at a minimum allow, the teachers the opportunity to step up. The alternative of doing nothing will just embolden the psychopaths hell bound on destruction.

We're assuming the killer is as accurate as Chris Kyle. The alarm goes off and the doors close. The shooter knows that behind each door is an armed teacher. Armed with what? What level of training? Who knows? Might be a former vet teacher, might be a newbie college grad teacher. Hard to say.

America's only real holiday is Black Friday. Remember the two lady's choking each other in Macy's over a purse? How about the grown man that shot a college age kid over an X-box (or similar) in Walmart? You don't hear stories about that anymore do you? Why? Because from November 1st to February 1st, we enter a time period known as: "the holiday season." And during "the holiday season" stores are allowed to generously bend the rules, security wise. Mall cops are allowed to be armed, stores that don't normally have security, suddenly do, etc. Now think about your life and how you act. Has your teenage daughter EVER come home crying "OMG I LIKE SO COULDN'T SHOP AT THE MALL BECAUSE ALL OF THOSE GUNS KEPT DISTRACTING ME."

No. You've never heard that. Have you yourself ever come home "early" from a black Friday event because of "too much security?" No. You've never done that either. So the bottom line is that you, the American, have learned to...

LIVE WITH GUNS

during the time period from November to February. So here's an idea: extend the holiday period. Instead of November 1 to February 1, make it November 1 to October 31. Make it all year. Extra armed security everywhere. Snipers on the roofs at sporting/concert events. Metal detectors in theatres and libraries. More armed cops in schools. Now, note that in nations like England, France and Australia that have "successfully" (LOL) banned guns, crime has never truly gone away, has it? So yes, there will still be crime. But hopefully the crime will be like it was in Pearl, Mississippi where the young moron stood up, announced his intention to kill and the fully armed vice principle drew his .45 and took him out.

The Dallas police faced a shooter from an unknown position, the situation in school shootings is that the shooter is in the same room or hallway, so the range advantage of a rifle doesn't offer a distinct advantage. While the focus in recent shootings have be AR's, handguns are still the most likely weapon and again, no range advantage. I would see no reason that a reasonably trained amateur couldn't be a real deterrent.
The other thing to consider is that mass murderers do not pick victims that can fight back.

LCpl Timothy McCain Why not try it? The alternative is to let more students get killed. Not all teachers, but some, especially veterans could respond. The police officer will have to answer why he did not respond. If I was a teacher with a weapon, I would have no problem confronting this shooter. Keep in mind that most of these shooters are not professionals.