Teachers With High Licensing Scores Found More Effective

San Francisco

Students whose teachers score high on state licensing exams learn more mathematics over the course of a school year than peers taught by teachers with low scores, according to a new study that draws on 10 years of test-score data on North Carolina schoolchildren.

Coming at a time when experts and policymakers are divided over what makes a "highly qualified" teacher and how to produce one, the findings provide important evidence that teacher-licensing exams may be meeting their purpose in screening out ineffective teachers. But Dan D. Goldhaber, the University of Washington researcher who did the analysis, said his study also found a downside to some such tests: They keep some good teachers out of the classroom, too.

"There are clear trade-offs states are making in using these tests," said Mr. Goldhaber, a research associate professor at the university, located in Seattle. "So it really...