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James Cabot and Julia Cabot seem like the kind of law school students high-paying law firms like to recruit.

Their resumes and work experience are nearly identical. Both of them attend respected institutions and have worked their way to the top 1 percent of their classes. Their schools aren’t among the very top-tier institutions where the big firms do most of their recruiting ― Harvard, Yale, et al. ― but they’re still well-regarded.

What’s more, James and Julia clearly come from economically advantaged backgrounds, the kind that firms admit make candidates a strong “cultural fit.” On their resumes, James and Julia each note their interest in classical music and polo. They both mention their experience on their college sailing teams. When people talk about “elites,” they’re talking about people like James and Julia Cabot.

Yet when law firms looked at their resumes ― which, again, were totally the same but for their gender ― recruiters were three times more likely to call James in for an interview, according to a study first published last year in American Sociological Review and recently written up in Harvard Business Review.

In a follow-up survey and interviews, the researchers learned that lawyers discounted Julia Cabot’s credentials ― indeed, the credentials of any economically advantaged woman ― because of a belief that she would eventually leave the workforce to become a stay-at-home mom.

In other words, for some women, there’s a “motherhood penalty” before they’re even thinking about becoming a mother. This old-fashioned notion exists even though a majority of mothers are now in the workforce. And the stereotype, according to this study, clings mainly to economically advantaged women.

As you may have already guessed, James and Julia Cabot aren’t real people. They were invented for the purposes of the above study. And while it may be hard to conjure much sympathy for the polo-playing Julias of the world, this kind of stereotyping is likely part of the reason why, despite achieving relative equality in education, women have largely failed to reach the uppermost ranks of power in the business world.

“This is a key mechanism that is keeping women out of high-paying occupations,” Lauren Rivera, a professor at Northwestern University’s Kellogg School of Management and a co-author of the study, told The Huffington Post.

Firms are screening out high-performing women not because of something they’ve done or haven’t done, but because of the firms’ own speculation about what they might someday do. The reasons for doing this “are completely in the heads of organizations,” Rivera said.

American Sociological Review The researchers signaled class on resumes by listing certain athletic accomplishments and extracurricular activities.

It’s already well-known that women’s careers and incomes suffer when they become moms. Female employees who become mothers see their salaries decline by 4 percent, according to one survey. Men who become fathers, by contrast, see their salaries rise by 6 percent. But there’s less hard evidence of a pre-motherhood penalty. Indeed, the wage gap between women and men is at its smallest when women are first out of college and haven’t yet married or had children.

Yet any woman who’s thought twice about wearing a wedding ring to a job interview would probably not be shocked to learn a pre-motherhood penalty exists.

Even at progressive companies that say they value hiring and promoting women, the default assumption is still that a woman will want to downshift her career once she becomes a mother, if she can afford it.

Women make up a majority of law school students in the United States, but only around 20 percent of law firm partners. Most firms are quick to speak of the need to hire and retain more women, to diversify.

The researchers devised a second pair of candidates to go along with the Cabots ― James Clark and Julia Clark, who both hailed from less well-off families. Or at least, that’s the impression their resumes, which mention their interests in country music, pickup soccer and track and field, were calculated to give off.

The researchers didn’t choose these characteristics because of any data that shows law firms tend to hire expert sailors or discriminate against country music fans. They were simply trying to signal that a person did or didn’t come from money. They even conducted an online survey to make sure their choices sent the right message. Polo signaled fancy elite rich kid; pickup soccer, not so much.

It’s standard practice to include extracurriculars and outside interests in law school applications. You might not even get considered for a job without including such things.

The point of the study was to drill down and see what effect social class has on hiring at high-end firms. Rivera, who has written a book on how elite investment banks and consulting and law firms favor entry-level workers from upper-class backgrounds, wanted to do more strictly quantitative work on this issue ― to try and isolate class as a factor in the hiring process.

“It was hard to know from interviews if employers were truly discriminating or just picking the best and brightest,” she said.

A lot of the research on class assumes that education is a great equalizer ― that once you’ve got a degree from a top school, your background doesn’t matter that much to potential employers.

But “it does matter,” Rivera said. “It matters quite a bit.”

The study doesn’t even get into the ways that race and ethnicity intersect with class in employers’ minds. The resumes in this study were presumed to be from white candidates. Black, Hispanic and Asian women and men face different sets of stereotypes and biases, and Rivera wants to do further research there.

For the study, the resumes from James and Julia Cabot and James and Julia Clark were sent to 316 offices of 147 leading law firms around the U.S. The goal was to apply for summer associate positions ― internships at law firms that pay around $3,000 a week and typically lead to full-time job offers once the candidate finishes school. Those entry-level positions pay a stunning $150,000 a year (not counting the bonus) and offer a fast track to the 1 percent.

The researchers expected that the upper-class candidates would get called back at higher rates than the candidates whose personal info telegraphed “lower-to-middle-class.”

That’s not exactly what happened.

James Cabot, the upper-class man, was offered an interview at 16.25 percent of the firms, a rate that far outstripped everyone else. Polo-playing Julia Cabot saw a 3.8 percent callback rate, while country music-loving Julia Clark got a 6.3 percent callback rate. The lower-class male candidate, James Clark, only got a 1.3 percent callback rate. The researchers say the differences between the women and the lower-class man were not statistically significant.

American Sociological Review The higher-class man was by far the preferred candidate of law firm recruiters.

It’s worth noting, Rivera said, that law firm recruiters skew male and tend to be a little older ― factors that may have had some bearing here. Still, she was surprised to find class offered no advantage to women.

In a follow-up survey, Rivera and her colleagues asked 200 lawyers around the country to look at the four mocked-up resumes and give their feedback. In that survey, the upper-class man was again viewed as the most favorable candidate.

The authors then personally interviewed 20 lawyers for their thoughts on the resumes. Those interviews yielded a gold mine of various stereotypes about white men and women of different economic standings.

There was concern that neither James nor Julia Clark would fit in at a high-end law firm. Some of the lawyers even suggested the lower-class candidates would be better suited to public interest law.

James and Julia Cabot, with their privileged backgrounds, were seen as a good fit for a law firm. “If you look at the interests, it’s classic cultural capital,” one lawyer told the researchers.

However, the lawyers questioned Julia’s commitment, wondering if she “really wanted to be a lawyer,” the researchers write in their paper. Some declared she was “biding her time” until she could become a “stay-at-home mom.”

American Sociological Review The candidates' resumes offered clues by which they could be stereotyped. Many lawyers took the bait.

James Cabot, on the other hand, was seen as a good long-term bet.

“An upper-class man is always going to be working,” a lawyer named Betsy said. “He’s always gonna stay in the workforce, and chances are he’s well connected, and that might be a good person to have at your firm.”

The important thing to note here, Rivera said, is that men and women both tend to leave big law firms after their first three or four years working there. Firms hire far more associates than they could ever hope to bring on as partners. In other words, even if a firm hired Julia Cabot and Julia Clark and they both left after a couple years, it wouldn’t actually make much difference to the firm.

“[Firms] expect most people to leave,” Rivera said. “It’s a pyramid organization. A tournament predicated on the fact that lots of people are going to leave.”

Interestingly, the gender bias wasn’t an issue for Julia Clark. Coming from a less advantaged background, she was viewed as “hungry” for work. She would have “mouths to feed” and “law school debt to pay,” the lawyers told the researchers.

Perhaps this is a sign that hiring managers can overcome some gender stereotypes. But it’s probably best not to wait around for that day.

Rivera says if we want to avoid this kind of stereotyping, law firms should stop asking candidates to put extracurriculars and interests on their resumes.