Is California's "API Growth" A Good Measure Of School Performance?

Matthew Di Carlo:

California calls its "Academic Performance Index" (API) the "cornerstone" of its accountability system. The API is calculated as a weighted average of the proportions of students meeting proficiency and other cutoffs on the state exams.

It is a high-stakes measure. "Growth" in schools' API scores determines whether they meet federal AYP requirements, and it is also important in the state's own accountability regime. In addition, toward the middle of last month, the California Charter Schools Association called for the closing of ten charter schools based in part on their (three-year) API "growth" rates.

Putting aside the question of whether the API is a valid measure of student performance in any given year, using year-to-year changes in API scores in high-stakes decisions is highly problematic. The API is cross-sectional measure - it doesn't follow students over time - and so one must assume that year-to-year changes in a school's index do not reflect a shift in demographics or other characteristics of the cohorts of students taking the tests. Moreover, even if the changes in API scores do in fact reflect "real" progress, they do not account for all the factors outside of schools' control that might affect performance, such as funding and differences in students' backgrounds (see here and here, or this Mathematica paper, for more on these issues).

Posted by Jim Zellmer at January 8, 2012 1:54 AM
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