Bernice Sandler, “the godmother of Title IX” who passed away on Jan. 5 at age 90, had one big regret about the landmark law she helped enact.

Though Title IX makes it illegal for colleges to discriminate on the basis of sex, it also contains a big loophole, one that allows some of the most elite, liberal colleges to discriminate against female applicants.

Academically, girls outperform boys by a wide margin. Nationally, 70 percent of high-school valedictorians are girls. According to the College Board, girls account for 60 percent of all high-school students with A or A-plus averages despite taking harder classes than boys, even in math and science.

This is reflected at the nation’s top public universities. The University of California-Berkeley accepted 15 percent of men in 2018 versus 19 percent of women, according to US Department of Education Data. At the University of Michigan, it was 24 percent for men and 29 percent for women. The University of Virginia was 26 percent for men and 28 percent for women.

But it’s a different story at many of the nation’s top private colleges. Yale, for instance, has had higher acceptance rates for men than women 14 out of the last 15 years. Vassar College’s acceptance rate in 2018 was 35 percent for men versus 19 percent for women. At Georgetown, it was 18 percent for men and 14 percent for women. At my alma mater, Brown, it was 10 percent for men and 8 percent for women.

Why the discrepancy? Back in 1972, when Title IX was being debated, admissions officers believed women attended college to get Mrs. degrees, not prepare for careers. As a result, elite colleges like Harvard and Yale pushed to exempt undergraduate admissions at private colleges (but not public) from Title IX’s ban on sex discrimination.

Congress gave in — much to Sandler’s dismay.

“I’m still unhappy about it,” said Sandler, a professor turned women’s rights activist, in 2016. “It does mean that some of the men [who] are accepted aren’t as smart as some of the women they turn away.”

While the notion of an Mrs. degree now seems silly, the same private colleges still use the exemption to engineer gender balance on campus. They believe colleges become less attractive socially when female enrollments approach 60 percent.

I understand why some deans — particularly those who grew up during more genteel times — might prefer a more balanced campus. Colleges with 60 percent-female enrollment ratios do tend to have wilder hookup cultures, as revealed in my book “DATE-ONOMICS.” Dating cultures are more promiscuous and less monogamous when ratios skew female.

It would be interesting to see if the Ivy League would support a repeal of the Title IX loophole

Thing is, colleges are institutions of learning, not matchmaking services. I also don’t see much evidence that applicants are shying away from 60 percent female colleges. Both NYU and Boston University are 60 percent female, yet both schools had record numbers of applications last year.

Back in 2006, Kenyon College’s then dean of admissions, Jennifer Delahunty Britz, admitted discrimination in an op-ed for The New York Times, writing that the “standards for admission to today’s most selective colleges are stiffer for women than men.”

Of course, not every private college has been as willing as Kenyon to acknowledge discriminatory practices.

Asked in 2016 whether men were being favored, Brown’s dean of admissions told The Brown Daily Herald there’s “nothing deliberate” about the university’s 15-year history of lower acceptance rates for women.

In 2008, Yale’s dean gave much the same answer to The Yale Daily News, insisting that his admissions officers “make no explicit effort” to manipulate Yale’s gender ratio.

Given how Ivy League schools have circled the wagons lately to support Harvard in the face of Asian-American applicants accusing the school of bias, owning up to discrimination may not be in their collective DNA.

But it would be interesting to see if the Ivy League — generally so quick to tout pro-female initiatives and curriculums — would support a repeal of the Title IX loophole. I believe a repeal would make things fairer for women.

The godmother of Title IX did too.

A former senior writer for Fortune, Jon Birger is the author of “DATE-ONOMICS: How Dating Became a Lopsided Numbers Game” (Workman Publishing), out now.