Racial preference policies in college admissions were always meant to be temporary and, after almost half a century, may soon come to an end.On Nov. 6, Oklahoma became the eighth state to ban affirmative action at public universities. The vote followed oral argument last month in Fisher v. University of Texas at Austin, in which the Supreme Court exposed the central unfairness of racial preferences -- and hinted at what might come next.The key exchange came when Justice Samuel Alito pressed the University of Texas on its use of racial preferences for wealthy minorities. When a lower court banned UT from using race in admissions, it began admitting graduates in the top 10 percent of every high school and giving a preference to economically disadvantaged students -- programs, Alito noted, that produced significant racial and ethnic diversity.Texas later reinserted racial preferences into the mix, arguing in part that, because those admitted through the 10 percent plan were more likely "to be the first in their families to attend college," racial preferences were needed to admit students such as "the African American or Hispanic child of successful professionals in Dallas" who defy stereotypes.Alito said, "I thought that the whole purpose of affirmative action was to help students who come from underprivileged backgrounds."The dirty little secret of higher education, however, is that selective universities are more interested in admitting fairly affluent students of all colors than in promoting social mobility.The court may be poised to jettison its deference in the 2003 case of Grutter v. Bollinger, in which the justices took the University of Michigan law school "at its word" that race-neutral methods of admissions would not produce sufficient racial diversity.The facts give reason to think race-neutral programs can succeed. A Century Foundation report that I co-authored found that seven of 10 leading universities nationwide were able to match or exceed racial and ethnic diversity achieved using racial preferences. The three exceptions are universities that draw on a national applicant pool and face a hard time enrolling black and Latino applicants when competitors still provide racial preferences.If the Supreme Court curtails the use of race, much as it struck down school integration programs in Seattle and Louisville in 2007, universities are likely to react the way school districts have: by focusing on economic disadvantage.A shift toward economic affirmative action would represent an enormous change in university admissions. Although many colleges claim to provide a boost to low-income applicants, as they do for minorities, data show that most selective colleges and universities may not.In 2005, William Bowen and his colleagues found that being black or Latino increased one's chances of admissions by 28 percentage points but that being low-income increased one's chances not at all.Likewise, Anthony Carnevale and Stephen Rose of Georgetown University found in 2004 that racial affirmative action tripled the representation of African-American and Latino students, compared with admissions from a system based on grades and test scores, but that those in the bottom economic half received no boost.It would be better if universities seeking diversity had to vigorously pursue race-neutral alternatives such as socioeconomic affirmative action first and use modest racial preferences as a last resort. Research from 2010 suggests that socioeconomic obstacles to doing well on standardized tests such as the SAT are seven times as large as racial obstacles.Low-income and working-class students ought to be able to do the course work. Carnevale and Rose concluded that the nation's 146 most selective institutions could almost quadruple the representation of students from the bottom socioeconomic half and graduation rates would remain unchanged. Likewise, Texas's experience suggests that students admitted through race-neutral alternatives can perform quite well.Addressing class inequality in university admissions could be costly and could open uncomfortable conversations about preferential treatment for the children of alumni, who are disproportionately well-off. A conservative Supreme Court decision curtailing the use of race in admissions could help move our country toward a more progressive version of affirmative action, one that gets at root issues of class inequality that higher education would rather avoid.Richard D. Kahlenberg, a senior fellow at the Century Foundation, is the author of "The Remedy: Class, Race and Affirmative Action" and editor of "Rewarding Strivers: Helping Low-Income Students Succeed in College."