No matter what you think about last week’s Supreme Court decision blessing state bans against using race in college admissions, the ruling will have a certain outcome: More states will consider bans.

Ohio, Missouri and Utah already have ballot measures teed up. Within hours of the decision, a state legislator said he would introduce one in Wisconsin. Those states would join California and seven others, with about a quarter of the U.S. population, in banning race as a consideration in college admissions.

This is disheartening. Diversity in the U.S. is at risk as public schools re-segregate. The education achievement gap between whites and minorities, meanwhile, remains wide. The combination is setting back racial equality as fewer minorities graduate from high school, go on to college and get good-paying jobs.

Affirmative-action supporters need to make a better case to voters. They should start by conceding that class-based affirmative action, which considers family income and wealth but is blind to race, is less divisive than skin color in divvying up college slots. Yet they should also point out that class-based programs don’t necessarily maintain diversity levels.

Some states that use class-based methods have even lost ground, as Michigan has since 2006, when voters approved the ban the Supreme Court upheld this week. Black enrollment is down 33 percent at the University of Michigan, for example.

The results are equally disappointing for the University of California system, which has been barred from using race since 1996. Even after taking such steps as improving outreach to high schools and guaranteeing admission to the top 9 percent of students, diversity levels haven’t rebounded, the system’s amicus brief in the Michigan case says. These measures cost state taxpayers $500 million ― a point affirmative-action advocates should emphasize.

Class-based programs have worked in some states, but often due to rapid minority-population growth. As admissions officers have learned, income isn’t a perfect proxy for race. Because there are far more low-income whites than low-income blacks, using class-based standards can even make the racial balance worse. In addition, black and Hispanic students who attend challenging high schools and who aren’t in the top of their classes don’t benefit from so-called percentage programs like California’s.

What does seem to work is accepting somewhat lower test scores, considering parental education, awarding extra points if English isn’t spoken at home, and defining applicants as disadvantaged if their neighborhood is low-income but their household isn’t. Yet even then, racial diversity doesn’t always return to the level that existed before a ban.

Universities continue to add to these criteria. Eventually, they may find the right formula, but it’s important to note that the attractiveness of these criteria is their ability to increase racial diversity. In other words, numerous proxies are being applied with the intent of finding qualified black and Hispanic students. For now, why not just admit the qualified black and Hispanic students?

There is another important point backers of affirmative action could make: Primary schools are resegregating. In the 2010-11 school year, according to national test data, 42 percent of blacks and 38 percent of Hispanics attended high-poverty schools (where 75 percent of students get free or reduced-price lunches). Forty percent of minority children attended schools where the white population is 10 percent or less. Only 6 percent of whites and 15 percent of Asians were in high-poverty schools. Senator Cory Booker, the New Jersey Democrat, calls this “an apartheid of education.”

Meanwhile, data reveal a persistent racial achievement gap. In math, the average black eighth grader performs at the 19th percentile of white students and the average Hispanic student at the 26th percentile. Might re-segregation explain this? Researchers say it’s too soon to know, but they are worried.

A college education is the gateway to a decent income and the middle class. If education diversity declines, so will workplace diversity and ultimately racial equality. Dozens of large U.S. companies, for this reason, support race-based college admissions. As their Supreme Court amicus brief said, employers desire work forces that represent all races, religions and cultures because that is the world they must sell their goods and services to.

Affirmative-action proponents would do well to urge schools to adopt reforms, including ending programs that merely admit the children of wealthy blacks and Hispanics, along with legacy admissions that benefit the offspring of white alumni. Voters would be more open-minded if universities de-emphasized the use of race and better explained diversity’s social and economic benefits, from less racial stereotyping to lower poverty levels.

This isn’t naive. A recent Pew Research poll shows Americans overwhelmingly (63 percent to 30 percent) favor affirmative action to increase the number of minority college students.

In addition, proponents could lobby for states to allow more transfers to competitive state universities from community colleges, which usually have higher rates of minority enrollments. Still, race-based programs must continue, if only to supplement class-based measures, for the time being.

By Paula Dwyer

Paula Dwyer is a Bloomberg View editorial writer. She was previously London bureau chief for Businessweek and Washington economics editor for the New York Times. ― Ed.

(Bloomberg)