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In Chicago, students won't be heading back to class tomorrow, that's according to the city's teachers' union, which has been on strike since Monday. One of the main disputes is whether student test scores should be used to evaluate teachers and determine their pay. Mayor Rahm Emanuel is one of the many leaders around the country who say yes.
But as NPR's Tovia Smith reports, many teachers insist it's unfair to grade their teaching based on the performance of their students.
TOVIA SMITH, BYLINE: Just talking about how best to evaluate teachers is a huge leap in an industry where reviews have historically ranged from non-existent to an annual classroom visit from the principal, otherwise known as the drive by.
KATE WALSH: You know, teachers aren't used to being evaluated in an honest way.
SMITH: Kate Walsh, president of the National Council on Teacher Quality, says teachers have long been getting an automatic pass.
WALSH: This is a system where 99 percent of all teachers were being found to be satisfactory. You know, it's everybody gets a trophy.
SMITH: These days, even teachers agree that quality should matter. But on the question of using test scores to measure quality and linking quality to pay, not so much.
About two dozen states now mandate that some objective data, like standardized test scores, be a factor in teacher evaluations, but policies vary. About half the states make student test scores count for 50 percent of a teacher's grade. The others give it less weight or leave it up to local districts. And increasingly, student performance is being tied directly to pay.
No surprise, Walsh says, that in several cases the issue has landed in court.
WALSH: There is no way to avoid this conversation, if you want to put it in polite terms. A down and dirty fight, if you want to put it in uglier terms. But there's no question, getting there is going to be rough.
SMITH: Teachers argue it's unfair to blame them for a student's poor performance, when so many outside factors are at play. And, they say, there's so much nuance in what they do, like inspiring kids or teaching persistence, that the formula experts have developed to calculate a teacher's value, added from test doesn't work.
RICHARD IANNUZZI: I mean, it's not ready for prime time. So why would we directly connect it to decisions about tenure or salary?
SMITH: Richard Iannuzzi, president of the New York State United Teachers Union, says how well students do should not drive how well teachers are paid.
IANNUZZI: We don't pay doctors on the number of heart patients who survive heart surgery. That's not how we do business.
SMITH: Experts concede that teacher evaluation formulas are still a work in progress. But Dan Goldhaber, director of the Center for Education Data and Research at the University of Washington, Bothell, says algorithms are now sophisticated enough. They measure student improvement, not just scores, and they adjust for everything from socioeconomic factors to class size.
He says how much weight to give test scores is debatable, but they shouldn't be ignored.
DAN GOLDHABER: You know, the baseball analogy is probably apt. Batting averages vary from year to year. But I don't think anybody would say that we're not going to use it for anything. That's silly.
SMITH: Research shows that linking pay to performance doesn't really motivate weaker teachers to suddenly improve. But, Goldhaber says it does play a big role in improving faculty in general.
GOLDHABER: You change the mix by encouraging the right teachers to stay in the profession, and the right teachers to leave. And/or by creating informal learning. You know, a teacher, for instance, goes to talk to another teacher who got a big bonus and says, you know, what the heck are you doing to be so productive?
SMITH: But teachers argue collaboration would actually suffer, as they would be pitted against each other competing for better results.
Iannuzzi, from the New York State union, says that kind of competition is anathema to what teachers do.
IANNUZZI: I mean, it's just a different world in education. It is a world about lifting all boats. It's not a world about my battleship taking out your battleship.
SMITH: Iannuzzi says schools are rushing into what's being sold as a quick fix. But advocates say the stakes are too high to wait. As one put it, some decent teachers may be unfairly penalized, but that's better than bad teachers not being penalized, and a whole class of kids paying the price.
Tovia Smith, NPR News.