In yet another sign that the lack of teacher diversity is a pressing issue, a new study suggests that white teachers expect less academic success from black students than black teachers do from the same students.

The study, conducted by Johns Hopkins University, found that when a white teacher and a black teacher consider the same black student, the white teacher is 30 percent less likely to think the student will graduate from a four-year college. White teachers, the researchers also found, are nearly 40 percent less likely to think their black students will graduate from high school.

“One of [the teachers] has to be wrong,” Nicholas Papageorge, a co-author and economist in the Krieger School of Arts and Sciences, said in a statement.

It bears repeating that while it is true that high-school graduation rates are lower for black students, the discrepancy has to do with unequal access to opportunity and resources, not innate ability. Black students are more likely to attend high-poverty schools with fewer resources, and to have less access than their white peers to advanced-placement courses. Student-to-counselor ratios are also much higher than recommended, a problem that is particularly troubling for poor students, who are disproportionately likely to come from families that lack experience navigating the college-admissions system.

The research, which involved an analysis of data from the Educational Longitudinal Study of 2002, a national study of more than 8,000 10th-grade students, suggests that low expectations from some teachers might engender low performance from students. The researchers found that when black students had a non-black teacher in a particular 10th-grade subject, they were much less likely to enroll in similar classes subsequently, suggesting teacher bias may have long-term consequences. More than 80 percent of public-school teachers are white, and the vast majority are women. Efforts to diversify the nation’s teaching corps have been slow, despite vocal support from U.S. Education Secretary John King and teachers’ unions.

If a teacher does not expect a black student to do well, she may be communicating those expectations, even subconsciously, to the student. (The study says white teachers have especially low expectations for black boys.) “A teacher telling a student they’re not smart will weigh heavily on how that student feels about their future and perhaps the effort they put into doing well in school,” Papageorge said.

Charles McGee, the co-founder of the Portland-based Black Parent Initiative, and the father of two young children, says he isn’t surprised anymore when he sees studies like this one. “All the data and life experience suggest that this is the reality,” he said. “Our families have to figure out a way to advocate better for children, to really sort of transform the landscape.”

He points to recent successful efforts at Portland’s mostly black Jefferson High School to raise graduation rates. Between 2014 and 2015, the graduation rate jumped from 66 to 80 percent. The school has made a series of changes, including allowing students to earn college credit at nearby colleges while they are still in high school, and bolstering mentoring programs. The underlying belief, as McGee put it, is that “failure is not an option.”

As the researchers note, their findings likely have implications beyond school, into the workplace and the criminal-justice system. The researchers say they are studying how biased expectations might impact long-term outcomes for students, including employment and involvement with the criminal-justice system. Alleviating some of the bias or recruiting and retaining more teachers of color could reduce some of the achievement gaps between white and black students, and help propel more black students toward high-school graduation and beyond.

While McGee agrees that hiring more diverse teachers is a good thing, he thinks it’s just a start. “We’ve got to deal with racism and structural bias in all of these systems,” he said. “We have to attack them. We have to be bold about it.”