At a makeshift memorial, Denyse Christian, hugs her son Adin Christian, 16, a student at Marjory Stoneman Douglas High School, where 17 students and faculty were killed in a mass shooting Feb. 14  in Parkland, Fla. (Gerald Herbert/AP)

There likely aren’t many, if any, of the several million working teachers in the United States who haven’t done what the author of this post writes about — imagining what they would do if a shooter came into their classroom. If you think it’s an easy call, try again.

This was written by Peter Greene, who teaches English in a small town in Pennsylvania and writes the always lively Curmudgucation blog, on which this first appeared. He gave me permission to publish this.

By Peter Greene

What if the shooter came in right …. now?

Because this is the world we live in now, I’ve been conducting a little thought experiment for a few months. What would I do if a shooter entered my building, and if I were armed?

The thought experiment has been pretty simple. At various moments during my teaching day, I imagine that a shooter has just entered the building, maybe nearby or maybe in another wing of the school.

My campus is sprawling, and there certainly are scenarios in which an active shooter situation could play out so far away from me that I wouldn’t know about until it’s over. Or it is possible that I would learn about a shooter from an announcement or text or fleeing students. In that case, I would take my students and go running out of one of the two nearby exits.

I suppose in some of those scenarios I could grab my gun and head toward the shooter. I don’t know if I’m that brave, but I do know I would feel a primary obligation to stay with my own students and make sure that they had someone with them to help get them to safety and to help keep them from freaking out.

One of the things I immediately noticed as I started conducting this thought experiment was that the vast majority of the time, I am surrounded by students. If a shooter were to enter my room and I was on the other side, I would have to shoot past students to hit him (I always assume that it will be a him). If the shooter targets a crowded area, such as a school assembly or a lunch period, there would be students between us and behind him. In the hall between classes? More of the same.

In the vast number of scenarios that I imagined, I would have to be a well-trained sharpshooter with a weapon more accurate than a handgun to fire at the active shooter without hitting my own students.

Many of these scenarios would also require me to be carrying the gun with me at all times, which opens up its own set of scenarios that I did not really consider, other than to note that most of those scenarios are bad.

What if my class has enough warning to lock down in place, and I’m using the firearm to defend the door? This is a problem in my case because there are two doors into my classroom, and the take-cover area for my room would have to be the space between those doors. In other words, I would have to make a choice about which door to stand beside, and if I were to guess wrong, there would be students between me and the other door I would want to defend.

I could play this morbid game for weeks because there are so many alternative scenarios, and the specifics of each one make a huge difference. What if the shooter comes when students are doing a presentation, or doing group work spread out over two classrooms and the hall? What difference would it make if the shooter shows up during the period when my students tend to listen to me as opposed to the period when the students tend to dismiss everything I say?

And what would I do if, as is often the case, the shooter is a current or former student? Could I shoot at a student?

After conducting this thought experiment, I can say this: While I can’t say that a gun would never, ever be useful in a shooter situation, I can say that 98 times out of 100, it would not be helpful at all. And that’s just assuming I would be properly and regularly trained enough to stay relatively cool under pressure.

If I measure that against all the possible problems of having the gun on my person or in my room, I must conclude again that arming teachers is folly. Of course, the noise about arming teachers has gotten much quieter since teachers started getting all militant with strikes and walkouts and gathering around the state capitol.

Why conduct this experiment at all? Because that’s the world we live and teach in now. Why did I stop the experiment? Same reason.

My wife came home recently after spending a half day learning about how to stop bleeding in a gunshot wound victim. She spent a half day learning about packing material into wounds so that her 10-year-old students would be less likely to bleed out in a nightmare shooter scenario.

That’s the world we live in — a world in which schools think about this stuff way too much. So I’m going to do my part by thinking about it less.

Thought experiment over. Don’t arm teachers.