In the weeks before the Supreme Court ruled on the constitutionality of Obamacare, the country trembled with anticipation. No such eagerness is evident now — yet the court is again poised to rattle our world. The case of Fisher v. Texas could upend the system of racial preferences in use throughout American higher education.

The pursuit of racial justice in education has arguably led to some benefits since its inception in the 1960s. But in the two generations that have elapsed since affirmative action began, evidence of its unintended consequences has accumulated — even as a society-wide taboo has forbidden honest discussion of that evidence.

The vast majority of elite American institutions supports racial preferences. Of 92 briefs filed in the Fisher case, 17 agreed with the plaintiff that racial preferences should be considered unconstitutional, while 73 urged that the current system remain undisturbed (two were in between). The pro-university briefs included submissions by the U.S. government, 17 U.S. senators, 66 members of Congress, 57 of the Fortune 100 companies, numerous education associations, colleges and universities and establishment organs, such as the American Bar Association.

Criticizing affirmative action — which is code for racial preferences — can be a career-endangering step for anyone, particularly for academics or politicians.

Some scholars have nevertheless been willing to follow where the evidence leads and have found that nearly everything we believe about racial preferences is wrong. In their outstanding book “Mismatch,” Richard Sander and Stuart Taylor Jr. document the paradoxical results of giving large preferences to racial and other minorities.

Sander and Taylor argue persuasively that the trouble with preferences is not the injustice done to people like Abigail Fisher, who was denied admission to the University of Texas while less qualified black and Hispanic applicants were accepted — though that is unfair — but also the harm it does to those to whom such preferences are extended.

Preferences have created a widespread mismatch between minority students and the schools they attend. Minority students at all levels — least so at the very top colleges — tend to wind up at schools for which they are less well prepared than the majority of their classmates. The University of Texas is typical in awarding the equivalent of hundreds of SAT points to minority applicants.

This results in minority students, who’ve been assured that they have what it takes to be successful, plunging to the bottom of the class. Students accepted under the preference regime often experience severe feelings of inferiority, social segregation and much higher dropout rates.

Both for affirmative action “beneficiaries” and their classmates, mismatch reinforces negative stereotypes. It also causes more African-American students to flee math, science and engineering majors in favor of softer subjects, such as education and sociology. “Black college freshmen are more likely to aspire to science or engineering careers than are white freshmen, but mismatch causes blacks to abandon these fields at twice the rate of whites.”

Yet research has shown that when minority students attend schools for which they are well matched, there is no attrition in demanding fields of study. It isn’t that minority students cannot make it as scientists and engineers, but simply that they conclude that they cannot succeed when forced to compete with superior classmates.

This phenomenon also accounts for the relatively low numbers of minorities who seek academic careers despite (or rather due to) five decades of preferences. It carries lessons for families considering whether to take advantage of “legacies” for their children. The research suggests that academic and career success is more likely when students attend colleges for which they are well matched.

Deciding who is a member of a historically oppressed minority group also gets trickier with every passing decade. Intermarriage is up. Immigration also complicates matters. A recent study found that 40 percent of African American Ivy League undergrads are first- or second- generation immigrants.

There is a place for preferences in higher education — for those who come from poor homes or tough neighborhoods. But there is abundant evidence that awarding preferences based on race and ethnicity is counterproductive, corrupt and profoundly unjust.