Daniel Katz of Seton Hall University explores the meaning of Sheri Lederman’s victory in court over New York State’s teacher evaluation system, the one promoted by former Commissioner John King (now Secretary of Education). He shows the complicated statistical calculations that produce “VAM” ratings and growth scores. Bruce Lederman, the attorney representing his wife in the proceedings, called them “a statistical black box.” It is not clear that anyone understands these models or can claim that they accurately measure teacher quality. This case is probably the first in the nation where a teacher has successfully overturned her rating.
Not only are these models difficult to impossible for teachers and most administrators to understand, they simply do not perform as advertised. Schochet and Chiang, in a 2010 report for Mathematica, found that in trying to classify teachers via growth models, error rates as high as 26% were possible when…
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