When black teachers and white teachers are asked to sum up black high school students' potential, white teachers are much less likely to see black students as college material. And that's true even when they're discussing the same students.

A new study exploring how race influences teachers' perception of their students' abilities found that those expectations are racially biased.

When teachers are asked about their expectations for black students, nonblack teachers were 30 percent less likely than black teachers to say they thought those students would earn a college degree.

The implications are troubling, in part because the majority of public school students in the US are nonwhite but the majority of teachers are not.

How racial bias influences teachers' expectations

On average, black students have lower test scores than white students, they attend schools with fewer resources, and they are less likely to graduate from high school and college. Assuming that will continue to be the case is what President George W. Bush called "the soft bigotry of low expectations."

But Bush was usually talking about collective expectations. The researchers in the new study, published as a working paper by the Upjohn Institute, which specializes in employment research, didn't compare teachers' broad expectations for their black students with their expectations of white students. It looked at how teachers of different races perceived the potential of the same student — where race, theoretically, shouldn't make as much of a difference.

In 2002, as part of a study that followed high school sophomores through the educational system, the Education Department asked those students' math and reading teachers if they expected them to eventually earn a high school or college degree.

The researchers, Seth Gershenson, Stephen B. Holt, and Nicholas Papageorge, looked at how those expectations differed based on whether the teachers were the same race or sex as their student, using a data set of about 16,000 students. They found that teachers' expectations for their white students didn't differ based on the teachers' race, but that black teachers' expectations were significantly higher for their black students than white teachers' expectations were.

The differences were even larger when the teachers were of both a different sex and race than their students — particularly for white female teachers evaluating black male students.

"We cannot determine whether the black teachers are too optimistic, the non-black teachers are too pessimistic, or some combination of the two," Gershenson wrote in a blog post at the Brookings Institution. "This is nonetheless concerning, as teachers’ expectations likely shape student outcomes."

The "Pygmalion effect": Teachers' expectations matter

Teachers' opinions can be a self-fulfilling prophecy. In a famous experiment, two researchers administered an intelligence test to students at the beginning of the 1968 school year. The researchers gave teachers a list of the students they said were most likely to make the most progress that year, based on their test results. At the end of the year, they tested the students again — and sure enough, at least in the first and second grades, the students on the researchers' list had in fact made the greatest intelligence gains.

But the students' names had been put on the list at random. They hadn't actually scored higher on the intelligence test than their classmates had. Their teachers just believed they were most likely to make progress, and possibly treated them differently as a result.

This might even be true for the students included in the new study. A different analysis of the same data from the Center for American Progress found that high school sophomores whose teachers expected them to graduate from college were more likely to eventually do so, even after controlling for other factors.

The results from the new study are particularly concerning because many students are taught by teachers of a different race. About 82 percent of teachers in the US are white, compared to about 49 percent of students; only 6 percent are black, although 15 percent of students are.

The researchers say their findings shouldn't be taken as a condemnation of white teachers. Instead, they say, they're a reminder of the power of implicit bias to shape our expectations and, eventually, reality.