As summer turns to autumn, the hallowed halls of academia fill with eager, young minds thirsting for an opportunity to study with thoughtful professors, engage in vigorous and civil debates about the Great Books or the Founding Fathers, and immerse themselves in these venerable laboratories of learning where future citizens are groomed.

Back in our new, warped reality, any parents who think their children are experiencing this once-common campus environment today might want to ask for a refund. Speech is no longer free, and in some cases it’s downright dangerous.

Today’s campus protesters make the college radicals of the 1960s look like boring conformists. Henry David Thoreau’s concept of civil disobedience is out the window. There’s nothing civil about the aggressive and violent nature in which today’s students are shutting down free speech at America’s colleges and universities. And their professors? One was recently charged with four counts of felony assault for donning a black mask and clocking Trump supporters with a bike lock.

A Brookings Institution study revealed ominous signs about the threats to free speech in this country. Some 1,500 students at colleges and universities were surveyed about various ways that a speaker on campus might be stopped. Shockingly, 19% of them responded that violence is an acceptable method of shutting down a speaker.

Lest readers assume this is a partisan problem, the survey shows that among undergraduates, 20% of Democrats, 22% of Republicans and 16% of Independents believe that violence is an acceptable way to silence opponents.

So far, however, it is leftists who are turning this violent mindset into action against disfavored speakers. Sadly, this violence is becoming commonplace as a way to stifle free speech and the expression of uncomfortable ideas.

Sen. Chuck Grassley (R-IA) wrote in The Daily Signal about Middlebury College in Vermont, where “the eminent scholar Charles Murray was at first shouted down from speaking, then when the event was moved, students pulled the fire alarm to prevent him from speaking.” Grassley notes, “It was not Murray but the students who essentially falsely yelled ‘fire’ in a crowded theater. The Middlebury professor who moderated the debate was physically assaulted, and has yet to fully recover from her serious injuries.”

Grassley added, “It was not a mere handful of students but a mob who engaged in such appalling conduct at an institution theoretically devoted to rationality and intellectualism. Not including those who were not captured on video, the college disciplined more than 70 students. But none were expelled or even suspended.”

The response from authorities at colleges and universities has been disgraceful, which only invites future acts of violence. And while many professors are turning a blind eye, others are actually encouraging students to resort to extreme measures in order to shut down free speech.

While these purveyors of violence want us to believe that they’re somehow protecting the community from vile ideas, the average American would be surprised by what they consider hateful and offensive. Joshua Fatzick writes at Voice of America that “students at Claremont McKenna College in California targeted Heather Mac Donald,” author of The War on Cops. Why? Because her book “puts forth the idea that police officers are afraid to perform their jobs because of increased media scrutiny following the 2014 police shooting death of Michael Brown in Ferguson, Missouri.”

So how did we get here? This is a complex question.

Part of the problem is that many students simply don’t know what’s in our Constitution and are unable to identify even one of the freedoms in our Bill of Rights. Without the knowledge that our Constitution protects all speech, even that which expresses ideas contrary to our own beliefs, students are engaging in tactics that not only threaten civil discourse in academia but also threaten our very constitutional system.

The Brookings survey also showed that 44% of college students believe that the Constitution does not protect what is considered hate speech (only 39% believe it does). Robby Soave at Reason writes, “Teenagers are somehow making it through 12 years of primary education without absorbing the most basic civics lesson: The founding documents of the United States of America zealously protect people who make offensive statements from censorship at the hands of government officials or violent mobs.”

One might argue that the Brookings report and other similar surveys distort or exaggerate the degree to which college students are opposed to free speech. The only problem is that professors, students and campus organizations no longer speak in subtle terms about their objectives, but directly challenge our founding documents and values. For years, these views were expressed as a manifestation of our constitutional rights. Now they’re being violently defended in order to oppose our constitutional rights.

Take, for instance, this year’s Constitution Day lecture at Princeton University, in which anthropology Professor Carolyn Rouse argued that “the academy has never promoted free speech as its central value.” Rouse went on to state that it’s up to institutions to determine what they believe to be free speech, “and therefore have their own internal rulemaking capacity, with needs to induce or coerce compliance.” Think about it: We’re paying huge sums of money to have people like this teach our children.

One of the primary obstacles conservatives must overcome in restoring a broad understanding of our country’s principles and values is that our education system continues to politicize the teaching of history or simply ignores it completely.

Making matters worse is that far too many college students are not even aware of the purpose of a university education. Gone are the days when institutions of higher learning boasted of their role in creating free thinkers and future citizens primed to enter the real world as contributing members of a free society.

Peter Berkowitz in The Wall Street Journal asserts, “American colleges and universities should be bastions of self-knowledge and self-criticism, simply because they exist to teach people how to think. But in recent years America’s campuses seem to have abandoned this tradition. Worse, the meager course offerings on the topic of liberal education tend to reinforce misunderstandings about its character and content.”

Where we go from here is critical to the very survival of our basic rights and our Constitution. We can’t merely dismiss anti-constitutional rhetoric as an anomaly on the college campus or a product of aging left-wing professors clinging on to the radicalism of the 1960s. When college students will stop at nothing to silence opposing views, the academy is ill. It is diseased. No longer an issue of liberal or conservative, tomorrow’s leaders will exercise power with a far different notion of Liberty. Our Constitution, and the idea of free speech itself, is hanging in the balance.