Let’s imagine that Jason Moorehead was teaching a class about the 2020 election, and a student said it had been “stolen” by the Democrats. What would Moorehead do?

That’s the big question we should be asking about Moorehead, the Allentown social studies teacher who was put on paid leave after social media showed him participating in the “Stop the Steal” rally that preceded the U.S. Capitol insurrection on Jan. 6. His school district says it is conducting a “formal investigation of his involvement” in the protest. But it should pay much more attention to what he has said in the classroom, especially now that Moorehead is pushing to return there.

Moorehead’s attendance at the protest coupled with social media posts suggest that he thinks the election was stolen (though he has since claimed he meant to promote no such notion). One post shows a picture of himself wearing a “MAGA” hat and carrying a Revolutionary War flag, with the caption, “Doing my civic duty.”

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Of course, Moorehead has the same right as any other American to express what he thinks. But he has no right — none — to spread falsehoods in his own classroom. And he also has the duty to rebut students who embrace them.

A biology teacher cannot tell her class that the Earth was created in six days, or that vaccines cause autism. An environmental studies instructor can’t say that human-made climate change is a hoax. And a history teacher must not declare that the Holocaust never happened.

Even more, teachers should correct these claims when students make them. It isn’t enough to let them slide, or to pretend that there are “two sides” to these questions. They’re not questions at all. They’re myths, distortions, and lies.

So what did Jason Moorehead do, when the election came up in his own classroom? We don’t know yet, of course. But his recent comments to CNN’s Michael Smerconish should give us pause.

“I definitely have some conservative values and beliefs, but they have never taken part in what I do in the classroom,” Moorehead told Smerconish. “I’ve always encouraged my kids to be critical thinkers and to form their own opinions, ones that they can be proud to have.”

But whereas everyone is entitled to their own opinions, as Daniel Patrick Moynihan famously said, they’re not entitled to their own facts. So our teachers have to be clear and explicit about which is which. Some statements are facts, which are beyond debate; others are opinions, which must remain open to it.

Did Donald Trump incite the Jan. 6 riot? Should he have been impeached? And what should the Senate do in response? Those questions should all be up for grabs in our schools because reasonable and informed people disagree about them.

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But reasonable and informed people do not disagree about whether the election was stolen. Nor do they debate whether Democrats are running a pedophile ring out of Congress, as QAnon adherents have imagined. Those aren’t opinions or facts; they’re lies. And it’s the job of our schools to teach the difference.

Did Jason Moorehead? Again, that’s the only question that matters here. Moorehead says he stayed “a mile and a quarter away” from the Capitol and didn’t actually storm the building, which of course would be grounds for dismissal. If that’s confirmed, we should stop talking about what he said or posted on Jan. 6. That will simply turn him into a free-speech martyr on Fox News and its friends.

This shouldn’t be a question of free speech at all — it’s one of education. As a citizen, Moorehead should be allowed to drive to D.C. and scream his lungs out in protest, about whatever he chooses. But as a teacher, he must tell his students the truth — as the best scientists and scholars have determined it — and correct them when they err. The issue isn’t what he said outside of class. It’s what he did inside of it.

Jonathan Zimmerman teaches education and history at the University of Pennsylvania. He is the coauthor (with cartoonist Signe Wilkinson) of “Free Speech and Why You Should Give a Damn,” which will be published in April by City of Light Press.