If you want to understand how thick the bubble around higher education is, try this experiment: Ask the parent of a 12-year-old if they think higher education is “sustainable.”

Most likely, they will think you’re referring to college costs, as in, “Is it sustainable for Fordham to continue to charge $65,000 a year? And will it be forced to stop before my child starts his freshman year?”

If you ask a college professor or administrator about whether his school is sustainable, he will most likely launch into a diatribe about the size of a university’s carbon footprint.

The sustainability movement on campus is really environmentalism gone wild.

As the authors of a new report from the National Association of Scholars explain, sustainability’s goals “go far beyond ensuring clean air and water and protecting vulnerable plants and animals. As an ideology, sustainability takes aim at economic and political liberty.”

Using language to obfuscate is nothing new for the ivory tower, of course.

As Ohio University economist Richard Vedder points out, university campuses are the only places where an hour actually consists of 50 minutes. But the word sustainability seems to mean nothing and everything at the same time.

As a result, the campus sustainability movement has been able to infiltrate university life in a way environmentalism never could.

The NAS authors trace the launch of the movement to the “American College and University Presidents’ Climate Commitment,” which, among other things, required school leaders to promise to reduce their use of fossil fuels by 80 percent over a decade.

Not only was this not feasible, but it also meant that college presidents were acting far beyond their mandates, ignoring the interests of faculty, students and even oversight from the board of trustees.

Sure, the starting point is reducing climate change. But it quickly goes off the rails. Take a class at Cornell called “The Ethics of Eating.”

As one student explained: “This class demands one of two things: 1. That you defend the way you eat, or 2. That you change it. And in early February, I stopped eating meat because of what I’ve read, watched and learned in this class.” This is one of 403 courses Cornell has put under the rubric of “sustainability.” The others sound even sillier.

The NAS cites more: “Earthquake!” “Microbes, the Earth, and Everything;” “Race Social Entrepreneurship, Environmental Justice and Urban Reform;” and “Magnifying Small Spaces Studio,” which teaches students how best to live in mini-spaces and answers the question, “In reducing one’s carbon footprint, how small is too small?”

That’s a question that really gets to the heart of the sustainability movement, which is really about reducing the impact — indeed, the presence — of humans on Earth.

Proponents not only suggest eating less and consuming less energy, they want us to reproduce less, too. Because, well, fewer people use fewer things.

The NAS authors point out the “apocalyptic” tone of the movement, which uses the imminent demise of the planet as an excuse to restrict freedom.

As one of the movement’s proponents, Professor David Sherman, explains:

“Ecological services have little chance of surviving without tight control by law of human activity affecting the environment. This option would be thought of as totalitarian by today’s free societies, but this may be the only solution for us . . . The institution of liberal democracy fails to adequately address the challenges of the environmental crisis.”

What professor won’t rise to that bait?

The movement has spawned 50,000 books and 200,000 articles. There are now more than 100 formal organizations to advance sustainability on campus and 50 professional bodies for its experts.

There are more than 1,400 academic programs in sustainability at 475 campuses.

And none of that comes cheap, notes Vedder, who heads the Center for College Affordability and Productivity. “The costs of sustainability are very high compared to its benefits,” he notes: “Colleges are just doing a lot of this to feel warm and fuzzy.”

The NAS authors found the US government is spending an average of $465 million a year on sustainability research, mostly at colleges, and it’s been going up each year.

Not only are the costs being borne by taxpayers, colleges are also hiking student fees. NAS offers a case study of Middlebury College, which is spending almost $5 million a year on sustainability projects.

Sure, that’s only a little more than 1 percent of its annual budget, but in an era when the cost of college is already through the roof, is this really sustainable?

Naomi Schaefer Riley is a senior fellow at the Independent Women’s Forum.