The Detroit News reports that in the latest round of standardized testing, 11th graders enrolled in most of Detroit’s charter public schools did not outperform their peers in standard public schools in some subjects. Unfortunately, the story failed to mention a fundamental distinction that makes such broad-brush comparisons less meaningful than they appear.

Every student enrolled in a Detroit charter public school is there because of a deliberate choice made by parents. Because funding for schools is based on enrollment, charters must rely on the active choice of willing “consumers” to stay in business. In contrast, regular public schools are filled with students assigned to them on the basis of where they live. These schools essentially hold a monopoly on students who can’t get into a charter or another school of choice option (due to capacity limitations), or whose parents don’t try.

Parents choose charter schools for a number of reasons: perceived safety or social well-being, unique academic specialty, instructional delivery method, school culture or mission, emphasis on character building, etc. Ironically, some parents may select charters specifically because they de-emphasize standardized testing.

One result of all this is that the best measure of success for charters is not necessarily their performance on state-mandated standardized tests, but rather their ability to attract students. 

None of this is to say that Detroit charter schools are all perfect or that standardized test results don’t matter. In fact, test scores are and should be part of the calculation parents make in choosing a school for their children. That said, a charter school’s success or failure depends primarily on its ability to provide parents with what they want for their children, which might not always be higher average standardized test scores than nearby regular public schools.

While it might not please school bureaucrats or government employee unions who depend on regular public schools’ monopoly, the market-based system of accountability means that charter schools can’t survive unless they serve the interest of consumers — which in this “market” means parents and their children.