In our hyper-polarized era, calls to “keep politics out of the classroom” are routine. But public school classrooms are precisely the place where students should be learning how to discuss and debate contentious topics, according to a new book, The Case for Contention: Teaching Controversial Issues in American Schools, by Jonathan Zimmerman and Emily Robertson.

Since Donald Trump was elected, UPenn professor Zimmerman has been doing his part to argue for making controversy a part of the school day. In the latest episode of the Have You Heard podcast, AlterNet education editor Jennifer Berkshire and co-host Jack Schneider talk to Zimmerman about why bringing politics into the classroom has never been more urgent. The following is an edited transcript.

Have You Heard: We spend a lot of time these days bemoaning the state of free speech on college campuses. You argue that students basically arrive at college having no idea how to discuss and debate controversial topics because they never experienced it as K-12 students.

Jonathan Zimmerman: The skills that we're talking about here are skills of dialogue of liberation for reason of tolerance. They're not natural. Nobody comes out of the womb saying ‘I'm going to listen to you.’ In fact they come out saying ‘me me me.’ What we need to do as as parents as educators as citizens is teach them a certain set of skills about the way that politics and democracy is supposed to work. These are not natural skills. And it is clear from our current moment that we have a deficit of them. We're living in an incredibly polarized moment, a moment of mutual vilification, a moment where shouting is replacing talking and name calling is replacing discussion. And we will never be able to budge from that moment, we will not be able to move the needle unless our educational institutions step up to this challenge.

Have You Heard: Your book is also a history of how public schools have dealt with controversial issues. And it turns out that keeping politics out of the classroom was baked right into the original recipe.

JZ: Horace Mann himself wrote several articles and speeches insisting that schools should never address controversial issues. And the reason was that he was trying to build a system of free public schools, and more specifically, trying to get taxpayers to pay for the system. And his fear was that if they see what he called a controverted opinion—we would call it controversial opinion—especially one they did not share, they wouldn’t pay for his reform. And it's ironic. Schools themselves were born in controversy. The creation and the funding of schools was always controversial but they were not formed to discuss controversy inside their walls. Quite the contrary. The people who created them wanted to insulate them from controversy so that taxpayers would support them.

Have You Heard: You document how teachers have had periods of relative freedom to bring hot-button topics into the classroom vs. times where they’re essentially silenced—like during the build-up to a war. But all of the emphasis on standardized testing has taken a toll too.

JZ: There's no question that the whole accountability movement has played a constraining role, in part because the high stakes tests. It's not just that they increased teaching to the test, often they encourage teaching to a single right answer, which questions like ‘should we invade Iraq?’ often don't have. The other thing we've learned that's really important is that when you interview teachers about their professional preparation, learning how to address controversial issues is often not a part of their preparation at all. But controversial issues are part of democracy, and if our goal is for students to be able to agree to disagree, then teachers have to be prepared to lead those kinds of discussions.

Have You Heard: Since Trump was elected, you’ve undertaken a one-professor crusade to get students at UPenn to engage with other students across political lines. How’s it going?

JZ: I began organizing dialogues between college students from around the Delaware Valley after Trump was elected. I was really really upset by frankly the low quality discussion at UPenn, and by the frame of trauma that many people use to describe this which I think is kind of a rhetorical cul de sac, and something that inhibits discussion. And I decided that the only way we could really have discussion was by bringing in people from other places especially places with a different political profile than UPenn. So I got in touch with people at Cairn University, formerly Philadelphia Bible College and we organized a series of discussions between Penn students and students. Now we've expanded it to include students from Drexel, Villanova, Saint Joseph’s. One Penn student said in his evaluation that, "we're so afraid to talk to somebody of a different perspective and it turned out that it wasn't that hard."

Have You Heard: What do you think the students were so afraid of?

JZ: I think what they felt was a mixture of angry and scared. They understand that the political waters have in many ways been poisoned. But you can get people around a table from different positions and they can learn how to speak in simple and mutually respectful ways but they've got to do it and you've got to start somewhere. And I think that's the challenge right now. All of us are grappling with this I think in our own ways trying to make sense of that and trying to do little things that hopefully can not just promote dialogue but make a case for it.