As the political heat builds up to find a way to judge the competency of  teachers, the value-added modeling (VAM) statistical formula was created to answer the accountability call.

For a peak at the actual formula, and how it is affecting teachers, go to this article by Michael Winerip at the New York Times titled, “Evaluating New York Teachers, Perhaps the Numbers Do Lie.” Here you will also read about the huge amount of error in the scores, and how they can fluctuate wildly from year to year.

Since VAM will be used, indeed, has been used, to affect teacher’s careers, wouldn’t it be nice if it was shown to be a valid tool for assessing performance?  Unfortunately, this is not the case. As with so much education reform today, ideas are pushed into practice before the ramifications are fully known.

Los Angeles actually published a data base containing its teacher’s scores. For an excellent response to this public release of VAM scores please see: “True Value-Added Scores: Publish or Perish.” This article explains why posting such scores is not only unfair to teachers, but focuses on how the release of such information actually damaged the usefulness and validity of the scores. Here’s a taste of what Matthew Di Carlo says in this article:

Put simply, any time students are assigned to classrooms based on unmeasured factors, such as behavioral issues or motivation, that are associated with test performance, VAM results are corrupted. The extent of the bias that results from non-random assignment – the amount of inaccuracy it causes – is sometimes overstated (and simple random error, mostly due to small sample sizes, is arguably a bigger problem when there are only a few years of data), but it remains a huge issue in the use of these methods.

VAM is not without its supporters in high places, such as Bill Gates, billionaire and self-appointed education reformist, but that doesn’t mean it does what is claimed. The Economic Institute explored the use of test scores in teacher evaluation, and released the results in a briefing paper, which you can download here. In this paper, these researchers state:

Adopting an invalid teacher evaluation system and tying it to rewards and sanctions is likely to lead to inaccurate personnel decisions and to demoralize teachers, causing talented teachers to avoid high-needs students and schools, or to leave the profession entirely, and discouraging potentially effective teachers from entering it. Legislatures should not mandate a test-based approach to teacher evaluation that is unproven and likely to harm not only teachers, but also the children they instruct.

The paper is well worth the time to read through if you feel test scores are the way to go when evaluating teachers. It exposes many of the problems which laymen, including many of our politicians and self-proclaimed education reformers, are unaware.