At the Shanker Institute, a debate about value-added methods (VAM) for teacher evaluation was detailed on Twitter (@shankerinst), including comments from Tom Kane (Harvard) who makes two comments worth noting:

Shanker Institute ‏@shankerinst

Kane: Need to move from talking about WHETHER to use value-added and more about HOW to do so. #VAMuses

Shanker Institute ‏@shankerinst

Kane: Nobody arguing for using value-added as 100%, but arguments for 0% do not hold up scrutiny. #VAMuses

Kane’s first point is exactly wrong. In fact, we have left behind the whether long ago, without giving that key question the focus it deserved because, to his second point, the only percentage of VAM we should consider is, in fact, 0%. Why?

• A fundamental premise in statistics is do not use a metric for some purpose other than the one for which it was designed. Student tests are not designed to measure teacher quality.
• An ethical problem with VAM is holding one person (teacher) accountable for another person’s (student’s) performance.
• Campbell’s Law.
• What is tested is what is taught—the high-stakes accountability era has taught us that the more we focus on testing, the less we ask from teachers and students.
• The only fair way to implement VAM is to pre- and post-test every student in every class throughout the U.S. This is not justifiable in its cost in either time or money for the outcomes.
• Using VAM in any way incentivizes each teacher to use her/his students against the outcomes of other teachers’ students, possibly the most ethically damning aspect of VAM.

VAM is a tremendous waste of time and energy on one aspect of schooling (teacher quality) that is, at best, a minor measurable component of student learning. Committing to how to implement VAM also further detracts time and money better spent on the 85-90% of correlated factors in student outcomes—specifically the 60+% associated with conditions beyond the control of the school or the teacher.

For statisticians, VAM is a playground. But for the real-world of education, it is fool’s gold, an inexcusable waste of time and funding.

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Common misunderstanding: Teachers do not CAUSE learning. Teachers create opportunities to learn #VAM0%