Jon Birger is a freelance writer, a contributor to Fortune magazine and the author of "DATE-ONOMICS: How Dating Became a Lopsided Numbers Game."

Students on the campus of Duke University in Durham, N.C., on Friday, March 26, 2010. (Jim R. Bounds/Bloomberg)

Getting accepted to an elite college has never been more difficult. So to all the young women who got in this year I say: Great job! You earned it.

To the young men I say: Congrats. But just be thankful you didn’t have to apply as a woman.

Why? Because one of academia’s little-known secrets is that private college admissions are exempt from Title IX’s ban on sex discrimination—a shameful loophole that allows some of the most supposedly progressive campuses in the nation to discriminate against female applicants.

Consider my own alma mater, Brown University. In 2014, 11 percent of men were accepted at Brown versus 7 percent of women, according to U.S. Department of Education data.

Brown is hardly the only, or the worst, offender. At Vassar College, the 34 percent acceptance rate for men was almost twice as high as the 19 percent rate for women. At Columbia University, the acceptance rate was 8 percent for men versus 6 percent for women. At Vanderbilt University, it was 15 percent versus 11 percent. Pomona College: 15 percent versus 10 percent. Williams College: 21 percent versus 18 percent. This bias in private-college admissions is blatant enough that it can’t be long before “gender-blind admissions” becomes the new campus rallying cry.

Colleges won’t say it, but this is happening because elite schools field applications from many more qualified women than men and thus are trying to hold the line against a 60:40 ratio of women to men. Were Brown to accept women and men at the same rate, its undergraduate population would be almost 60 percent women instead of 52 percent—three women for every two men.

For students who attend public colleges and universities, the playing field is more level. Admissions at state schools are regulated by Title IX, which bans sex discrimination at undergraduate programs receiving federal funding. According to the U.S. Department of Education’s civil rights office, “public coeducational undergraduate institutions … must not discriminate on the basis of sex in admissions.”

Given that girls generally outperform boys in high school—girls earn better grades and account for 70 percent of valedictorians—you’d expect acceptance rates for women to be higher than for men. Indeed, women are admitted at higher rates at such top public universities as U.C. Berkeley, Ohio State, Penn State, Michigan and UVA. At the University of Georgia—which, in 1999, lost a legal challenge to its old practice of awarding extra points to male applicants—women are now accepted at a 57 percent rate versus 53 percent for men.

One notable—and by comparison, glaring—exception is the College of William & Mary. A public school in Virginia, William & Mary had a 28 percent acceptance rate for women in 2014 versus 42 percent for men. When former dean of admissions Henry Broaddus was asked to explain this back in 2007, he acknowledged that admissions were influenced by gender: “We are, after all, the College of William & Mary, not the College of Mary & Mary,” he said.

Today, William & Mary claims that the men and women it accepts are equally qualified, but its graduation rates tell a different story. Among undergrads who enrolled during the 2008-09 academic year, 84 percent of William & Mary women completed their studies within four years versus just 72 percent of the men, according to Virginia’s State Council of Higher Education.

William & Mary aside, women do enjoy a fairly level playing field when applying to state schools. So why are private colleges and universities still allowed to discriminate?

I posed this question to Bernice Sandler—the women’s rights activist who led the fight for Title IX—while researching my forthcoming book, “DATE-ONOMICS: How Dating Became a Lopsided Numbers Game,” which explores how women-heavy gender ratios in college affect dating and marriage outcomes after college. Sandler explained that when Congress first began debating Title IX, Harvard, Princeton and Yale demanded an exemption for private-college admissions. Given the Ivy League’s outsized influence, the only way to get Title IX passed, she says, was to relent.

The reason private colleges wanted the exemption in 1972 is different from the reason they utilize it today. Back then, too many admissions officers operated with the now-laughable assumption that women primarily matriculated to get their “Mrs.” degree. Today’s officials know better. They fear though that if enrollments reach 60 percent women, it will scare off the most sought-after applicants, who generally want gender balance for social reasons. “Once you become decidedly female in enrollment, fewer males and, as it turns out, fewer females find your campus attractive,” Kenyon College’s dean of admissions, Jennifer Delahunty Britz, wrote in The New York Times in 2006.

Such fears seem misplaced: UNC Chapel Hill’s undergraduate student body is approaching 60 percent women, and applications there have risen 35 percent since 2010—clearly, gender balance isn’t the only factor that potential students weigh. And while it might be a cliché, my reporting suggests that straight men at colleges with 60 percent women are perfectly content with a dating market that has three women for every two men.

In this context, I understand why Britz and others think they need to admit more men. But aiming for 50:50 gender balance is no excuse for discrimination against women in the college  application process. Men certainly aren’t a protected class meriting affirmative action to redress a past disadvantage, and college isn’t a matchmaking service. Students, and women in particular, can decide for themselves whether they wish to attend schools with 60 percent women—which is why Congress should act to strip private colleges of their Title IX exemption.

If the leadership at private colleges truly believes they need more men, they have other options. Consider the University of Rochester, a private university in upstate New York (where my brother-in-law happens to be a professor). With an undergraduate population that is 52 percent women and 48 men, Rochester is more balanced than most (the average ratio among undergrads at U.S. private colleges is 59:41). Yet women there are still admitted at a higher rate than men: 37 percent to 36 percent. One reason is that Rochester offers robust programs in science and engineering—fields that, for better or for worse, tend to draw more men.

Of course, gender balance isn’t why Rochester invested in these fields, but even if it were, building computer labs and hiring engineering faculty would be a far costlier way to achieve it than just allowing admissions officers to put their thumbs on the scales. Barring a change to Title IX, my own belief is that private colleges won’t stop discriminating until employers realize that not all college credentials are earned equally.

So if you’re a recruiter for a Fortune 500 company and two Vassar résumés come across your desk—one from a woman, the other from a man—keep this in mind: It was almost twice as hard for the woman to get into Vassar as it was for the man.

Maybe they’re equal candidates. But if you’re playing the odds, I’d say hire the woman.