Orwell Award Announcement SusanOhanian.Org Home

[Susan notes: Stephen Krashen mentions something most people ignore: Value-added loses all credibility when one thinks about how how test scores can be pumped up without any increase in student learning.]

Submitted to USA Today but not published

To the editor

"States weaken tenure rights for teachers" (Jan. 25) 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.


Not stable: Sass, T. 2008. The stability of value-added measures of teacher quality and implications for teacher compensation policy. Washington DC: CALDER. (National Center for Analysis of Longitudinal Data in Educational Research.) Kane, T. and Staiger, D. 2009. Estimating Teacher Impacts on Student Achievement: An Experimental Evaluation. NBER Working Paper No. 14607 http://www.nber.org/papers/w14607;

Different tests result in different value-added scores: Papay, J. 2010. Different tests, different answers: The stability of teacher value-added estimates across outcome measures. American Educational Research Journal 47,2.

Stephen Krashen, professor emeritus, USC

This site contains copyrighted material the use of which has not always been specifically authorized by the copyright owner. We are making such material available in our efforts to advance understanding of education issues vital to a democracy. We believe this constitutes a 'fair use' of any such copyrighted material as provided for in section 107 of the US Copyright Law. In accordance with Title 17 U.S.C. Section 107, the material on this site is distributed without profit to those who have expressed a prior interest in receiving the included information for research and educational purposes. For more information click here. If you wish to use copyrighted material from this site for purposes of your own that go beyond 'fair use', you must obtain permission from the copyright owner.