“Ivory Tower” delves into the loan debt crisis faced by college graduates — and looks at campuses that experiment with ways to teach that don’t also bankrupt those enrolled. (Samuel Goldwyn Films)

One trillion dollars. That unfathomable number — the amount of student loan debt we’ve managed to rack up — hovers ominously over the economy. And, unlike the housing crisis, there’s no option for foreclosure. Bankruptcy won’t make the bills stop coming.

How did we get here?

Andrew Rossi’s documentary “Ivory Tower” gets to the bottom of that while examining another hot topic: Is higher education, with its skyrocketing price tag, worth it? After all, as the movie shows, some parents are basically bankrolling little more than four years (or more) of keg stands and frat parties.

One of the most interesting discoveries is that it’s not just students who are in debt. In the spirit of competitiveness, colleges have had to up the ante. If one school has a rock-climbing wall, then the others need one, too. The same goes for bigger stadiums, better pools and cushier housing.

But in Rossi’s travels, from Columbia University to Bunker Hill Community College, Stanford to Spelman, he uncovers different approaches to higher education, where experimentation is working and kids are learning — without going bankrupt.

One of those places is Deep Springs, a two-year, all-male college on a California cattle ranch. Tuition is free, but students are expected to do manual labor between lectures about Nietzsche and Hegel. The documentary also spends quite a bit of time at Cooper Union in New York City, where, until recently, tuition was nil. But when the school tried to keep up with the Joneses (or at least the Harvards), and underwent a massive, costly remodeling, the board had to rethink the gratis approach. The decision was met with a months-long student sit-in in the president’s office.

“Ivory Tower” covers a lot of ground, and sometimes the focus feels diffuse. There are so many tricky issues — from massive, open online courses and high administrative salaries (according to the movie, the University of Chicago’s president made an astounding $3.3 million in 2011) to the Silicon Valley approach to education, which generally involves dropping out — that it might not have made sense to try to cover them all. And although some subjects are compelling — including a formerly homeless Cleveland kid attending Harvard on a full academic scholarship — they don’t always speak precisely to the point of the documentary.

Meanwhile, we don’t get much information about rankings, which is a major part of the equation. If all of these schools are pouring money into bells and whistles for the prestige of a top spot in U.S. News and World Report, it would be helpful to know just how those rankings are done.

In a democracy, education is paramount, and the student loan crisis is a problem on various fronts. Having so many millennials in deep debt is bad for the economy, of course, but worse still is what they may not have gotten for their not-yet-earned cash: the knowledge and critical thinking skills to advance our society.

★ ★ ★

PG-13. At Landmark’s E Street Cinema. Contains obscenity and partying. 90 minutes.