Graduates of Bowie State University put messages on their mortarboard hats during the school’s graduation ceremony at the Comcast Center on the campus of the University of Maryland, May 17, 2013 in College Park, Md.  (Photo by Chip Somodevilla/Getty Images)

(Editor’s note: After this story was published, a quote from Professor Jane Arnold Lincove found to be confusing. Lincove e-mailed a clarification, which is reflected in the text below.)

Setting aside, for a moment, the debates about diversity in higher education, here is a non-controversial statement: The purpose of the college admissions process is to screen for good students.

Standardized tests, GPAs, and recommendation letters should all offer insight into how someone will do in college. The College Board, which designs and administers the SAT, argues that the test is highly predictive of a student’s college GPA and likelihood of graduation. High school performance also matters, though high school GPAs also depend on how tough your high school was.

Tangled up in these measures are the issues of race and socioeconomic status. One argument for affirmative action is that people from different backgrounds perform differently on some standardized tests, not for reasons of intelligence or potential, but because they are not prepared. Likewise, it may be unfair to penalize a student for taking few AP classes if her high school didn’t offer many in the first place.

Context matters

So the task of a college admissions officer is complex. Not only do the hard numbers matter, but so does the context of a student’s upbringing. A recent working paper from three Texas economists aimed to measure precisely how these factors interact.

The researchers — Sandra Black and Jane Arnold Lincove of the University of Texas at Austin, and Kalena Cortes of Texas A&M — took advantage of an uncommonly rich source of data. They had records for all students in public Texas high schools, and college records for all of those who went on to a public Texas university.

In Texas, students who graduate in the top 10 percent of their high school class automatically have the right to attend any public Texas university, more or less. They still have to take the SAT or ACT, but the score doesn’t matter. This unusual situation meant that by studying this group of students, the researchers could measure how effective those tests are at forecasting future college performance without the muddling effects introduced by a typical college admissions system.

The most surprising result is that for black students, the SAT is a far more important predictor of college GPA than for white or Latino students. (This is after controlling for a host of factors including the choice of college major.)

For white students, scoring one-standard deviation higher on the SAT or ACT (that’s roughly a couple hundred points on the SAT) is associated with a college GPA that’s 0.347 points higher. For black students, higher standardized test performance is associated with an additional 0.152 point boost in college GPA. For Latino students, there was no additional boost.

Even though black students do worse on standardized tests on average, each additional point seems to be more valuable for them. “This speaks to the idea that affirmative action in admissions might empirically be a good idea,” Lincove said.

Looking beyond test scores

Lincove speculates that test prep is one reason that the SAT or ACT is less effective at predicting the performance of white students. The point of an SAT course is to learn how to score better, regardless of one’s own ability. Those who have more access to these resources are more likely to look better on paper, without actually being better students.

As the authors write in the paper: “These results suggest that the differential admissions process used in affirmative action would enable a more accurate assessment of student potential for success than a process based on a single set of objective criteria applied across racial groups.”

The Supreme Court has repeatedly discouraged public universities from explicitly holding students of different races to different standards. Colleges have to be subtler than imposing different SAT requirements for students of different races.The University of Texas at Austin, for instance, which was the center of a landmark ruling in 2013, practices what it calls a “holistic” review process for students who don’t make it in under the 10-percent rule.

But more and more colleges around the country are starting to experiment with transparent ways to admit students. At the University of Mississippi, for instance, state residents are guaranteed a spot if they meet certain GPA and SAT/ACT requirements. The researchers argue that these test score policies might end up excluding able black students. In these situations, the careful consideration of an admissions officer might lead to much more equitable outcomes than hard rules.