As I reported last week, Ohio charter schools received a bad rap in recent articles by The Economist. After singing the praises of charters in some of America’s largest cities, The Economist went on to disparage Ohio’s charters, stating that they “have done badly.” I didn’t disagree with their appraisal.
Why the agreement? It’s because the standard matters.
So in Ohio, charters are "bad" compared to what standard? To answer, I take a slice of data from Cleveland to look at the performance of its charter schools relative two comparison groups. First, I compare how Cleveland’s charters stack up against Cleveland Municipal School District (the city’s traditional public school). Second, I compare Cleveland's charters against a broader set of public districts--all districts in Cuyahoga County, which includes Cleveland Municipal, poorer inner-ring suburban districts, and some affluent suburban districts.
I use the fourth grade math proficiency rate—essentially, the proportion of students who “pass” Ohio’s annual standardized test in a given grade and subject—for the 2010-11 school year. And by using what’s called a “z-score” in statistics, I calculate how far each school's proficiency rate is above or below the average proficiency (pass) rate. A school...