Let the teachers teach

President Trump on Thursday repeated his call for “highly trained” schoolteachers to pack heat in their classrooms. If they were armed, the president said, they could fire back immediately at school shooters like the young man with an AR-15 semiautomatic rifle who took 17 lives in Parkland, Fla. Beyond that, he tweeted, the knowledge that teachers have guns of their own would deter “the sicko” from heading to a school in the first place. With his usual fondness for capital letters, he added, “ATTACKS WOULD END!”

Thus did Mr. Trump parrot a tired shibboleth repeated once again on Thursday by Wayne LaPierre, the executive vice president of the National Rifle Association. “To stop a bad guy with a gun, it takes a good guy with a gun,” Mr. LaPierre told a gathering of conservative activists. Actually, it’s hard to tell who was parroting whom. The president said much the same in a morning tweetstorm that said “a ‘gun free’ school is a magnet for bad people.”

Let’s ask someone who’s in the trenches every day what he thinks of arming teachers. “It’s hard to begin to count the number of ways this is a bad idea,” said Chris Magnus, police chief of Tucson.

For starters, the number of gunslinging educators would be huge. In the United States, there are about 3.5 million elementary and secondary school teachers in public and private institutions. Arming 20 percent of them, as Mr. Trump suggested, would mean 700,000 or so teachers with Glocks and the like on their hips — an armed force half as large as America’s real armed forces on active duty. One can envision parents with the means to do so swiftly yanking their children out of that sort of environment.

More to the point, many deranged mass murderers expect to die themselves during their killing sprees. It’s almost laughable to believe that the president’s proposal would deter them.

“Why would we think someone who has those kinds of problems is going to make rational decisions based on the fact that someone in the school might be armed?” Chief Magnus said.

And then there’s this inescapable reality: Teachers are human. It means they would most likely react to stress-induced fear the same as anyone else, with unintended consequences that could put even more people in peril.

You want people highly trained in the use of firearms? The New York Police Department has about 36,000 of them. Generally, despite an impression held by some people, they are restrained in firing their weapons. But in high-stress situations, they’re human, too. “Police officers miss a lot in combat situations,” said John Cerar, a former commanding officer of the department’s firearms and tactics section.

Nationwide statistics on police shooting accuracy are not to be found. But if New York is typical, analyses show that its officers hit their targets only one-third of the time. And during gunfights, when the adrenaline is really pumping, that accuracy can drop to as low as 13 percent. While Mr. Cerar thinks armed teachers could provide some deterrence, he said that experience shows, “Whatever you do, there’s going to be a problem associated with it.”

One problem is shooting bystanders. It isn’t routine, but it does happen. To cite just one example, from 2012, two New York officers shot and killed a gunman on a busy street outside the Empire State Building. But they also wounded nine other people who were hit directly or struck by shrapnel from ricochets.

It takes little imagination to foresee a situation in which a frightened teacher, thrown into a combat situation — in a crowded space like a school hallway or classroom — wounds students in the process of trying to take out a gunman.

The best way to prevent the threat of a bad guy with a gun is to keep him from getting the sort of battlefield weapon the Parkland killer used, by banning assault weapons and highcapacity magazines, and by tightening background checks.

In his remarks, the mendacious Mr. LaPierre said gun restriction advocates seek to “eradicate all individual freedoms.” In fact, sensible gun laws would give people, especially children, a better chance to enjoy the first of the inalienable rights mentioned in the Declaration of Independence: life.