Effective teachers can be identified by observing them at work, measuring their students' progress on standardized tests and asking students directly what goes on in the classroom, according to a comprehensive study released last week.
The three-year, $50 million Measures of Effective Teaching study, funded by the Bill & Melinda Gates Foundation, found it was hard to predict how much students would achieve in a school year based on their teacher's years of experience or knowledge of pedagogical technique.
But researchers found they could pick out the best teachers in a school and even predict roughly how much their students would learn by using a formula that equally weighed student input, test scores and detailed classroom observations.
Taken alone, each of those measures was fairly volatile. Judging teachers by student performance on state tests, for instance, turned out to be unreliable and inconsistent. Judging teachers by a principal's observations also didn't identify who could be counted on to boost student proficiency on state math and reading tests.
Combining all three measures into a properly weighted index, however, produced a result "teachers can trust," says Vicki Phillips, a director in the education program at the Gates Foundation.
The study comes at a time of bitter political wrangling over teacher evaluations in cities like New York, Los Angeles and Chicago -- and provides ammunition for all sides.
Education reformers who have been pressing to dismantle tenure systems protecting veteran teachers from layoffs could take heart in the finding that seniority doesn't predict classroom success.
Yet the report also bolstered union leaders who argue that teacher evaluations shouldn't be tied so heavily to value-added measures -- complex algorithms that gauge whether students do better or worse on state tests after several months in a given teacher's classroom.
Scores across the states
The Obama administration has pushed states to give heavy weight to quantitative measures such as test scores in designing teacher evaluations. More than a dozen states have moved in that direction — in some cases making it impossible for a teacher to earn a good review if his or her test scores are low, no matter how well the teacher performs on other measures. States including Florida, Louisiana, Colorado, Michigan and Ohio have been particularly aggressive in tying teacher ratings to test scores.