WASHINGTON, Sept. 1 (UPI) -- A report by education researchers suggests the value-added method of evaluating teachers, increasingly common in U.S. schools, may be unreliable.
The method compares students' year-to-year test scores to determine how much improvement individual teachers have been responsible for. Hundreds of school systems now use it, including large ones like New York, Washington and Chicago, and the Obama administration is pushing for rigorous evaluation.
Edward Haertel of Stanford University, one of the authors of the report, told The New York Times teachers' rankings can change sharply from year to year depending on what model is being used.
"People are going to treat these scores as if they were reflections on the effectiveness of the teachers without any appreciation of how unstable they are," he said.
Other critics say teachers can be judged by the performance or lack of performance of children who were in their classes for a few weeks. Teachers of high-achievers may also be short-changed if evaluations are used to determine salaries or bonuses because their students are less likely to show year-to-year improvement.
William Sanders, an analyst with SAS, a North Carolina evaluation company, has been working on value-added systems for almost 20 years.
"If you use rigorous, robust methods and surround them with safeguards, you can reliably distinguish highly effective teachers from average teachers and from ineffective teachers," he told the Times.
