NEPC Review: New York Charter Schools Outperform Traditional Selective Public Schools: More Evidence that Cream-Skimming is Not Driving Charters' Success (Manhattan Institute , March 2017)
A common argument leveled against charter schools is that they attract the most motivated and intelligent students from already struggling public schools. Marcus Winters seeks to examine this claim, known as “cream-skimming,” by comparing the performance of New York City’s (NYC) charter middle schools with a set of traditional selective public middle schools, which admit students on the basis of prior performance. Findings indicate that, controlling for student characteristics, charter schools perform no differently in English Language Arts (ELA) and significantly better in math than selective schools. Based on this, the report concludes that the success of NYC charter schools cannot be explained by cream-skimming. While on its face this conclusion may seem logical, the report suffers from two primary flaws. First, it assumes that selective school applicants are higher performing and more motivated than charter school applicants. This is unlikely to be the case because all students are required to apply to traditional middle schools in NYC, while applying to a charter school requires navigating an additional application process. Second, the report relies on a single year of data to make comparisons of ill-defined and inappropriate outcomes—an approach that does not address either the question of cream-skimming or charter school success. As an evaluation of cream-skimming in charter schools, this report misses the mark.