Little hands. A bad tan. And blood coming from wherever.

If you’re put off by the crude tone of politics in the Age of Trump, you’re not alone. According to a recent poll by Weber Shandwick, Powell Tate, and KRC Research, 70 percent of Americans think that political incivility has reached “crisis” levels.

The poll also found that Americans avoid discussing controversial questions, out of fear they too will be perceived as uncivil. The findings speak to a flaw with civic education, especially in the main institution charged with delivering it: public schools. Put simply, schools in the United States don’t teach the country’s future citizens how to engage respectfully across their political differences. So it shouldn’t be surprising that they can’t, or that that they don’t.

Schools have sometimes been blamed for the meteoric rise of Donald Trump, whose legions of supporters allegedly lack the civic knowledge to see through his proposals to ban Muslims from entering the United States or to kill family members of terrorists in the fight against ISIS. But it’s hardly clear that Trump supporters are less knowledgeable than anyone else. In six state GOP exit polls, Trump was the most popular candidate among college-educated voters and came in second in another six polls.

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. ...