A recent report from the Manhattan Institute seeks to demonstrate that “cream-skimming”—sorting students to favor smarter, harder-working pupils—is not the reason charter schools outperform traditional public schools on standardized tests. Author Marcus A. Winters points out that critics who use this argument ignore the fact that not all traditional public schools are open enrollment.
The report compares the English and math test scores of ninety-eight selective non-charter middle schools whose students have to pass entrance exams to be admitted, with those of seventy-three charter middle schools whose students are admitted by lottery and are often underprivileged minorities. All of the schools are located in New York City.
Winters reasons that if admitting students with better academic credentials does indeed result in higher test scores, traditional selective middle schools would fare significantly better than lottery-based charter schools. That is not, however, the case.
The report finds that the charter school students did better in math (38.3 percent proficient) than their peers at selective middle schools (34.7 percent proficient); but worse in English language arts (24.6 percent at charters compared to 32.2 percent at selective middle schools). Yet, when Winters adjusted for student demographics, the difference in ELA proficiency shrunk to a gap that wasn’t statistically significant, and the math gap widened to 11 percentage points, with a 15 percent proficiency rate at the lottery-based charter schools, compared to a 4 percent rate at the selective middle schools.
It is worth mentioning that this analysis cannot account for unobserved differences, such as parental engagement, and is therefore only descriptive and does not prove the extent to which charter schools are responsible for their students’ success. However, Winters points out that there is research showing that students who attend New York City charter schools perform better than they would have had they attended their default traditional public school.
So although this report is not wholly conclusive regarding why students attending charter schools score comparably or better than traditional public school students on standardized tests in New York City, it does cast a shadow of doubt on the claim that “cream-skimming” is the key to charters’ success.
SOURCE: Marcus A. Winters, “New York Charter Schools Outperform Traditional Selective Public Schools,” Manhattan Institute (March 2017).
