Progressives are bracing for a devastating defeat in the Supreme Court’s upcoming ruling on the affirmative action case Fisher v. University of Texas. If the justices restrict race-based affirmative action, they will “erase 50 years of progress,” one activist declared in The Nation. That’s an overstatement, but there is wide agreement that such a ruling would decrease the number of black and Hispanic students enrolled at many U.S. universities.

According to a new study conducted by Stanford’s Caroline Hoxby and Harvard’s Christopher Avery, however, the college admissions and recruitment regime currently in place is hardly a paragon of fairness. In fact, it is utterly failing America’s most promising low-income students.

The study’s disheartening findings are summarized simply in the first sentence of the abstract: “The vast majority of very high-achieving students who are low-income do not apply to any selective college or university.” Poor kids — especially in rural areas — often don’t know about financial aid opportunities or want to stay close to home or have never met anyone who went to a top college.

As a result, just 34 percent of high-achieving students (defined as those with test scores in the top 10 percent and an A-minus grade-point average or higher) in the lowest income quartile go to any of the country’s 238 most selective institutions, compared to 78 percent of high-achieving students in the top income quartile.

But where does affirmative action come in? All things being equal, studies show that admissions officers at selective institutions do not give a boost to low-income applicants. But it could be worse than that: There are some indications that the current admissions and affirmative action regime actually creates barriers that prevent low-income students from even applying, contributing to the grim situation Hoxby and Avery present in their study.

Most selective colleges that practice affirmative action currently seem content with achieving cosmetic racial diversity within largely upper-income student bodies — “a version of diversity,” The New York Times’ David Leonhardt wrote last year, “focused on elites from every race.” However, if top colleges were explicitly barred from using racial preferences, they might be forced to weigh socioeconomic status, geographic location and other factors more heavily in the admissions process. They would also be likely to recruit in low-income areas more aggressively.

Referring to the Fisher case, the dean of admissions at the University of Virginia told the Times that “if there are changes to how we define diversity, then I expect schools will really work hard at identifying low-income students.”

I don’t think it’s a coincidence that the two of the most selective colleges that do not use racial preferences — UCLA and UC Berkeley — also have higher enrollments of Pell Grant recipients (generally, students with family incomes below $40,000) than any other U.S. institutions. The UC system, which voters barred from using racial preferences in 1996, has developed an effective model for attracting low-income students that other colleges, including Amherst, have drawn from.

I have generally been skeptical — but agnostic — on the question of affirmative action. If, however, a disruption of elite universities’ present affirmative action system is needed in order to pressure them to better serve America’s brightest economically disadvantaged students, I would unequivocally support it. Diversity isn’t just about skin color, and racial justice is not the only type of justice worth striving for.

Social mobility in America is at one of its lowest levels in our country’s history. Canadians and most Europeans enjoy more social mobility than we do. Americans born to poor families have an unacceptably high probability of being poor as adults. The collapse of upward mobility is nothing less than an affront to the notion of equal opportunity that has been central to our national consciousness since de Tocqueville.

By showing why tens of thousands of bright, low-income high school seniors each year don’t go to good colleges, the Hoxby and Avery study helps illuminate the obstacles to mobility in America. And as Slate’s Matt Yglesias points out, the study is in one sense a cause for optimism, because it shows how much potential could theoretically be unleashed with relatively straightforward reforms.

Perhaps doing away with race-based affirmative action should be one of those reforms. Perhaps an aggressive ruling against affirmative action in the Fisher case is needed in order to pressure colleges to recruit and admit low-income students in greater numbers. Racial balance is not as important an imperative as the restoration of the promise of upward mobility in America.