College is a surprisingly multifunctional institution. It gives some students a chance to go completely bonkers before being shipped off to sit in a cubicle for 50 years. It allows others to learn and expand their horizons (as if anyone still goes tens of thousands of dollars into debt purely for the pursuit of knowledge). But perhaps one of the least noted aspects of a college education is the way it can stomp social mobility.

Surely, this sounds strange. Virtually everyone (myself included) has gone on about how education is supposedly this “great equalizer,” as the trite phrase goes. The real answer is that it depends.

Education can help improve social mobility, but that doesn’t necessarily mean it always does.

A study released on Wednesday by the Brookings Institution discussed how getting a college degree is part of the “glass floor” for people from high-income families who don’t have especially impressive skills.

Both ends of the income spectrum are particularly sticky, and while having better cognitive abilities improves the odds that individuals will earn more later in life, superior mental capacities are most prominent among the wealthiest in society, Brookings’ data show.

Of all the people who remain well to do, 43 percent of them were expected to fall into lower income distributions. The most statistically significant variable that might explain this phenomenon was the presence of a college degree. Wealthy individuals who, based on their skills, are expected to earn substantially less than their parents are 23 percent more likely to remain well off if they have college degrees.

In this case, higher education helps the otherwise unqualified wealthy retain their prestigious position. That’s not to say a college degree can’t help the poor. It’s just much more conditional. Motivated and mentally adept people in low-income brackets have a 42 percent better chance of reaching the top when they have a college degree.

So sure, higher education can help people move up the income ladder. But even so, it takes much less effort and strain to remain at the top than to climb to the top due to many of the advantages children of wealthy parents enjoy, such as better access to high-quality preschool programs, living in safer homes and neighborhoods, and having parents with more leisure time to devote to them.

Obviously, there’s also the barrier posed by the growing cost of college, and in spite of Pell Grants and other forms of financial aid, even among low-income students, full-ride scholarships aren’t exactly a dime a dozen.

Even when students get to college, the inequalities tend to be pretty stark. An executive summary by the Georgetown University Center on Education and the Workforce acknowledged that while college enrollment has exploded for black and Latino students from 1995 to 2009, there is a serious split that exists between white and minority students.

“Whites have captured most of the enrollment growth at the 468 most selective and well-funded four-year colleges, while African Americans and Hispanics have captured most of the enrollment growth at the increasingly overcrowded and under-resourced open-access two- and four-year colleges,” the summary said.

Obviously, race and income aren’t perfectly correlated, but by golly, they’re typically closely related.

Through blocking access to resources, the higher-education system tends to block access to resources for the lower classes while reinforcing the position of the wealthy. Not much of a great equalizer.