If you want to be a principal in Tennessee, you have to pass a $425 licensure test.

But a new study by researchers at Vanderbilt University suggests that the test is a poor predictor of how effective you’ll be as a school leader. And if you’re a person of color, you’re less likely to pass the test, according to the data.

Tennessee is among 18 U.S. states and territories that require all principals to take the  School Leaders Licensure Assessment, administered by a national testing company. Ten years of data from Tennessee test takers was the basis for the study by Vanderbilt’s Tennessee Education Research Alliance.

Researchers found that principals’ scores on the licensure exam were unrelated to how successful they were on their performance evaluations, student achievement in their schools, and teacher survey ratings of school leadership. In fact, in some cases, a high test score correlated with lower evaluation ratings.

They also found that candidates of color were 12 percent less likely than similar white candidates to attain the required licensure score.

A lack of diversity in school leadership is a challenge in Tennessee. In 2016, some 20 percent of principals were non-white, compared to 35 percent of students.

That’s problematic, said lead researcher Jason Grissom. He cites other studies showing that teachers of color have lower turnover rates and better job satisfaction under principals of color, and that principals of color tend to expel or suspend students less often. Both impacts, he said, are tied to better student outcomes.

“Leadership diversity certainly seems to matter for teachers, and it matters for students as well,” Grissom said.

States might be able to justify the hit to diversity if the test offered valuable information, but Grissom said it doesn’t appear to do that.

“This is a really, really hard job,” he said. “In a way, it makes a lot of sense to have an exam on the front end to tell us who are good at these things and less good. … But it’s difficult to create a test that can capture all the difference facets.”

Tennessee requires the nation’s lowest minimum score to be licensed as a principal, meaning that the racial disparities in other states that use the same exam likely are much worse, Grissom said.

Paul Fleming, Tennessee’s assistant commissioner of teachers and leaders, said the State Department of Education has heard similar reports in the past. That’s why the state now has other requirements for aspiring principals, like having at least three years of acceptable experience as an educator, completing a state-approved instructional leader preparation program, and being recommended by the state-approved educator preparation program.

“The role of licensure more largely is to serve as a check on whether educators have demonstrated that they have the right knowledge base and skill set to be an effective educator, which is of course important,” he said. “However, we have other measures and supports for teachers and leaders once they are in those roles, like our TEAM evaluation model, school leader academies, and other professional learning opportunities, to determine effectiveness and support their growth.”