Amy Lawson, a teacher at Silver Lake Elementary School in Middleton, Del., teaches language arts to her class of fifth graders. (AP/Steve Ruark)
Amy Lawson, a teacher at Silver Lake Elementary School in Middleton, Del., teaches language arts to her class of fifth graders. (AP/Steve Ruark)

A Los Angeles judge outraged educators around the country this summer when he threw out California's law granting schoolteachers tenure, ruling that it kept incompetent teachers in classrooms with minority students. What teachers saw as a simple reward for difficult and important work had been declared, in essence, a law with disturbing racial impacts.

Now, a new working paper suggests that schools in Los Angeles often wind up putting children of color in classrooms with teachers who have less skill and experience than those who teach their white classmates.

The differences were slight -- enough to move the average black, Hispanic or Asian student one or two percentiles lower on standardized tests -- but statistically significant. Harvard University's Thomas Kane, one of the authors of the paper, already made some of the results public while testifying in the Los Angeles case, Vergara v. California.

The impassioned debate over tenure and compensation for teachers has continued in the months since the ruling. Just this week, the Obama administration asked states to come up with plans for distributing the best teachers equally among students, regardless of race or family income.

In an interview, Kane explained how teachers' contracts can affect where the best ones work. Teachers often don't want to teach in schools in impoverished neighborhoods, because the job is so much more exhausting than in schools where the students come from happier homes and are generally better behaved.

In a district such as Los Angeles, teachers with seniority might have a contractual right to transfer to a post of their choice. Younger teachers who are just learning the profession end up working with poorer students, who are also often students of color.

"Our schools serving our most disadvantaged students are the places where novice teachers get hired and broken in," Kane said. "Once they develop some experience, they move to other schools."

At the same time, black and Latino families tend to move more frequently, and as a result, schools often have to hire a new teacher late in the summer when these families' children unexpectedly fill a classroom.

It isn't clear whether these patterns hold in other districts. A widely cited study of New York City schools did not conclude that white students were getting better teachers. Yet despite these inconclusive results, researchers generally agree that white students are probably concentrated in the best teachers' classrooms.

Teachers at schools in poor neighborhoods have "a really hard job," said Jesse Rothstein, an economist at the University of California, Berkeley who has criticized the ruling on tenure in California.

"It's not crazy to think that they might want an easier job -- or maybe it's fairer to say, a less difficult job," he added.

Figuring out what to do about that is a problem that no one has quite been able to solve. The administration's notice to states this week offered little in the way of specifics about how to get the best teachers to where their talents are needed most.

Like many economists, Kane feels that skilled teachers who work in disadvantaged neighborhoods should be paid bonuses to encourage them to stay, but identifying the best teachers poses additional questions.

Educators and parents around the country are becoming frustrated with standardized testing, which many feel does not accurately measure how much students are learning and wastes their time in the classroom.