Need for better evaluation system
Published in USA Today, Feb. 7, 2012
The article "States weaken tenure rights for teachers" emphasizes the importance of evaluating teacher effectiveness. A major problem is that these evaluations are often based on students' gains on standardized tests, called "value-added" measures.
A number of studies have shown that value-added measures are very unstable: Teachers' ratings based on previous years are weak predictors of test scores at the end of a year with new students. A teacher who succeeds in boosting scores with one group will not necessarily succeed with others. Different tests can result in different scores for the same teacher.
Value-added evaluations also ignore the huge impact of factors beyond the teachers' control. Finally, there are ways of pumping up test scores without student learning, including teaching test-taking strategies and making sure weak students don't take the test.
Nobody objects to teachers being evaluated on their effectiveness. Using gains on standardized tests is a bad way to do it.
Stephen Krashen, professor emeritus; University of Southern California; Los Angeles