May 9, 2017

Sarah A. Cordes, (215) 204-6332,
Daniel J. Quinn, (517) 203-2940,

Understanding "cream-skimming" in NYC charters will require better data, review finds

EAST LANSING, Mich. (May 9, 2017) — In March, the Manhattan Institute released a report that explored the extent to which charter schools' success could be attributed to "cream-skimming" from struggling public schools in New York. The report claimed that NYC's charter schools performed better than selective non-charter public schools. An academic review of the report released today finds that the report is of limited use for policy and practice.

Sarah A. Cordes, Temple University, reviewed the report, New York Charter Schools Outperform Traditional Selective Public Schools: More Evidence that Cream-skimming is Not Driving Charters' Success, for the Think Twice think thank review project. Think Twice, a project of the National Education Policy Center, is funded by the Great Lakes Center for Education Research and Practice.

The report compared the aggregate test scores in math and English of NYC's charter middle schools with a set of selective non-charter public middle schools, finding that the charter schools performed no differently in ELA and significantly better in math. The report concluded that the success of NYC's charter schools could not be explained by cream-skimming.

In her review, Cordes says that the conclusions of the report seem logical, but the report suffers from two primary flaws:

  1. It assumes that selective school applicants are higher performing and more motivated than charter school applicants; and
  2. The report relies on a single year of data to make comparisons.

In her conclusion, she says that this report misses the mark in response to evaluating cream-skimming in NYC charter schools. She writes, "Addressing the question of cream-skimming in NYC charter schools will require the use of longitudinal student-level data and much more rigorous methods."

Find the review on the GLC website:

Find the original report on the web:

Think Twice, a project of the National Education Policy Center, provides the public, policymakers and the press with timely, academically sound reviews of selected publications. The project is made possible by funding from the Great Lakes Center for Education Research and Practice.

The review can also be found on the NEPC website:

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The mission of the Great Lakes Center for Education Research & Practice is to support and disseminate high quality research and reviews of research for the purpose of informing education policy and to develop research-based resources for use by those who advocate for education reform.

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