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[Susan notes: Use Stephen's letter to send your own.]

Submitted to Star Ledger but not published

To the editor

The Star-Ledger feels that we need a better way of identifying the best teachers, and recommends the use of "value-added" measures, based on gains students make on standardized tests. ("Assessing teachers: New Jersey can learn from Los Angeles," August 27).

There is an extensive research literature showing the problems with this kind of measure, including the fact that a rating done one year does a poor job of predicting next year's score increases, as well as the fact that ratings appear to be test-dependent: A teacher's rating based on one reading test will not always agree with the same teacher's ratings based on a different reading test. Also test scores are easily manipulated when teachers provide students with test-taking strategies, which result in higher scores without students learning anything.

Some writers feel that those opposed to the use of value-added measures are opposed to gathering data on teacher effectiveness. Not at all. The point is that value-added is a lousy way to evaluate teachers.

Some sources:

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

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