Indeed, the facile dismissal of all Trump enthusiasts as bigots or ignoramuses speaks to the most urgent problem in American civic life: the inability to communicate with people who do not share the same opinion. Trump himself epitomizes that trend, routinely vilifying his opponents as “losers” or “dummies,” or worse. And yet Trump's critics often use similar terms to tar his diverse array of devotees. This isn't a discussion; it's a shouting match.

Public schools aren’t merely expected to teach young people the mechanics of government: how a bill is signed into law, what the Supreme Court does, and so on. They’re also responsible for teaching the skills and habits of democratic life, especially how to engage civilly with people from a different political camp.

Many districts have written policies promoting the teaching of “controversial issues” in schools. Typically, these policies affirm students’ right to discuss such issues as part of their preparation for citizenship. They also warn teachers against imposing their own point of view on students.

But there’s an enormous gap between policy and practice. Many teachers say they’d like to address controversial issues but lack the time; in poorer districts, especially, every available minute is devoted to preparing students for high-stakes standardized tests. Others admitted that they were not prepared to lead such discussions, which require deep background knowledge on the issues as well as the skill to manage diverse opinions about them.

Still other teachers said that their districts discouraged or even barred them from addressing controversial issues, particularly if the teacher displayed a liberal or unorthodox bent. After the United States invaded Iraq in 2003, for example, two teachers and a counselor in Albuquerque, New Mexico, were suspended without pay for hanging posters in their classrooms urging “No War Against Iraq.” School officials invoked the district’s “controversial-issues” policy, which declared that teachers “will not attempt, directly or indirectly, to limit or control the opinions of pupils.”

As later court filings confirmed, however, the district offered no evidence that the teachers were trying to do that; instead, the mere expression of their opinion was taken as proof of their propagandistic intent. Never mind that military recruiting posters festooned other parts of the school, or that one of the suspended teachers had organized a debate between herself and a pro-war colleague. Her poster was an act of indoctrination rather than education, officials said, and it had to be stopped.

Meanwhile, lessons that propagate conservative positions generally go unnoticed. In Morristown, New Jersey, one teacher asked a mostly black group of students to write an essay about “why they should not fear the police.” As an African American pastor told local school officials, who had established a policy encouraging “open dialogue and discussion” of divisive issues, the assignment took a truly controversial question—whether blacks had reason to fear police—and answered it from the start, before any real dialogue or discussion could begin.