Every spring and summer, America’s school districts face a critical challenge: hiring a batch of new teachers.

For some districts, the first problem is finding enough educators to fill their classrooms. But for many others, the central issue is choosing among the candidates — and administrators are left to develop their own systems for using résumés and test scores to predict who will do the best job.

New research suggests that Los Angeles, at least, has found a better way.

In 2014, Los Angeles Unified School District redesigned its hiring process to carefully cull teaching applicants. Each prospective teacher gets several scores for measures like college GPA, a sample teaching lesson, an interview, and professional references. Candidates who earn 80 out of 100 points get passed along for consideration to school principals. (Principals can still request an applicant who scored below that benchmark to be added to the hiring pool.)

The paper, published through the group CALDER at the American Institutes for Research, found that teachers who scored higher made a bigger impact on student achievement, scored higher on the district’s evaluation system, and were absent for fewer days.

Los Angeles’ screening tests “appear to accurately discern several aspects of teacher quality,” write the researchers, Paul Bruno of the University of Southern California and Katharine Strunk of Michigan State University. “The district may therefore benefit from its policy of excluding most low-performing applicants from employment eligibility.”  

The study is limited to teachers who were actually hired by the district, so it’s impossible to know how teachers screened out by the system — likely, the lowest-scorers — would have done in the classroom. Instead, the researchers compared the performance of the teachers who were hired with relatively high or low scores.

The differences were statistically significant but usually small. For instance, a teacher who scored substantially above average was about half as likely to receive a low evaluation rating (though only about 4 percent of all teachers fell into that category).

The researchers also examined whether schools benefited from the new hiring system. Indeed, it seemed to lead to small test score bumps in schools with higher shares of newly hired teachers, relative to what would be expected under the old system.

One consideration the study didn’t address was the impact on teacher diversity. Other screening systems — like teacher certification rules — tend to disproportionately exclude candidates of color.

The research is the latest in a string of recent studies showing that the way schools make hiring decisions can make a small but meaningful impact on students — and that many districts could do a better job at it.

When teachers are hired after the first day of school, students have been shown to do worse on tests at the end of the year. Still, some large districts had hundreds of vacant teaching positions at the start of this academic year. (Los Angeles, notably, had very few.)

Other districts, like Washington, DC and Spokane, Washington, have also created screening processes that predict teacher effectiveness.

Yet recent research suggests that more districts are actually decentralizing hiring decisions so that principals have more control over which teachers they take on. This may help ensure a good fit between teachers and a school, something research shows is important.

At the same time, the Los Angeles study highlights the potential benefits of a more standardized approach. Principals still make the ultimate hire, but have to sort through fewer applicants to get there.

Paul Bruno, one of the study’s authors, said finding the right balance — between autonomy and centralization — is a key open question. “That’s something we don’t know a whole lot about: how best to make that tradeoff,” he said.