About that Charter Achievement Thing

September 18, 2019

Each year when AzMerit scores are published charter proponents celebrate the sector’s higher scores relative to district schools. While some charter schools excel, overall evidence does not support that charter schools perform better than district schools on an apples-to-apples comparison.

Jake Logan, President & CEO of the Arizona Charter Schools Association, along with Nina Rees, President & CEO of the National Alliance for Public Charter Schools, recently highlighted the achievement of charters in Arizona in an opinion piece (link) in the Arizona Republic.

The Grand Canyon Institute, a public policy think tank, has published several policy papers on the financial practices of charter schools and their regulatory oversight. Its research has focused attention on how charters spend their taxpayer dollars, including how much is being invested in their classrooms.

In Arizona, district enrollment is flat and while charters have captured enrollment growth, which is a huge success for the sector.  At nearly 20 percent of Arizona’s total public school population, a greater percent of students enroll in charter schools here than in any other state.

That said, the actual achievement data isn’t as good as presented. To claim that charter students perform better than district students requires a student-level comparison. Comparing aggregate scores isn’t valid.

Yes, charter students in aggregate perform better than district students on the AzMerit but aggregate data can only be controlled for one variable, e.g., ethnicity. A valid comparison requires that multiple differences between students be controlled for. For example, if, as appears to be the case, the Hispanic students in charter schools are more likely to come from families with higher incomes and are less likely to be English Language Learners then, of course, they would be expected to score higher than their district peers.

A better method is to look at the outcomes for district and charter students from a similar urban area with a set of demographic similarities and compare prior individual records of achievement on standardized tests. This allows for a virtually equivalent comparison of charter and district schools.

Once those adjustments are made, the charter sector underperforms compared to districts overall based on analyses by Stanford University’s Center for Research on Educational Outcomes (CREDO).