Use Caution with Value-Added Measures

When the New York City Department of Education released its Teacher Data Reports in February 2012, Pascale Mauclair found herself in the spotlight—for all the wrong reasons. The New York Post dubbed Ms. Mauclair, a 6th grade teacher at highly rated P.S. 11 in Queens, the "city's worst teacher." There was just one problem. It wasn't true.

First, the data were suspect: Of the seven 6th grade teachers in the same school, three received zero percentile scores, an unlikely scenario for a school rated in the 94th percentile of the city's public schools. Next, although Ms. Mauclair taught both math and English language arts, only six of her students had taken the language arts assessment, a number below the allowable reporting sample of 20 students. Her value-added rating was therefore based solely on the results for the 11 students who took the mathematics exam (for which the minimum reporting sample is 10 students). Such a small sample is prone to distortions. Further, her class consisted of immigrant students who were still learning English and who entered her classroom at different times during the year; some students took the exam when they had been in her class for just a few months (Casey, 2012; Clawson, 2012).

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