[lbo-talk] Recipe for "privatizing" schools

[Jordan Hayes]

So long as we're slinging links:

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http://www.nber.org/~schools/charterschoolseval/memo_on_the_credo_study.pdf

   "A Statistical Mistake in the CREDO Study of Charter Schools"

   Caroline M. Hoxby

   Stanford University and NBER

   August 2009*

                          Abstract

   A recent study of charter schools' effect on student achievement

   has been published by CREDO (2009). It contains a statistical

   mistake that causes a biased estimate of how charter schools

   affect achievement. This paper explains that mistake. Essentially,

   the achievement of charter school students is measured with much

   more error than the achievement of the controls, which are not

   individual students but are group averages of students in the

   traditional public schools. By using the achievement data as

   both the dependent variable and (lagged) an independent variable,

   the CREDO study forces the estimated effect of charter schools

   to be biased, and the bias is negative unless the CREDO data

   are very atypical of administrative achievement data. This paper

   also notes that the CREDO study violates four rules for the

   empirically sound use of matching methods to evaluate charter

   schools' effects.