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November 02, 2009
As reported above, 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.” And, as a group they have if academic performance is what matters.
Below I take a slice of data from Cleveland to look at the performance of its charter schools relative to 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 with a positive score has an above-average proficiency rate; vice-versa, a school with a negative score has a below-average rate.
Figure 1 shows how charters compare against their district peers. Each bar indicates a school: charters are shown in red and district schools in grey. The vertical axis indicates schools’ z-scores—again, indicating how far their proficiency rate is from the group average proficiency rate.
On the left chart (figure 1A), Cleveland charters are pretty evenly distributed above and below the average. Conclusion: Cleveland’s charters do just about the same as their district peers. So far so good; but remember, Cleveland Municipal is one of Ohio’s lowest-performing public school districts and even consistently ranks at the bottom of big urban district performance in the country. For now, put the champagne on ice—performing on par with Cleveland should be no cause for celebration for charters or its students.
When I expand the geographic scope to all Cuyahoga County (figure 1B), charters, as a group, fall below the average line and fewer remain above the average line. Note the greater density of the red lines below zero. The rise in the average proficiency rate when higher-performing suburban schools are included causes this downward shift. In other words, when the standard gets higher, charter students fall further behind. (Note, though, that some Cleveland charters compare well with the best schools in Cuyahoga County. But these remain the “Needles in the Haystack.”)
Figure 1: Fourth grade math proficiency rates, scaled to the average rate, 2010-11. (A) Cleveland charters versus Cleveland Municipal School District schools. (B) Cleveland charters versus Cuyahoga County public school districts, inclusive of Cleveland Municipal. Data source: Author’s calculations based on Ohio Department of Education data.
Have Cleveland’s charters “done badly?” Depends on your standard. To their credit, the Mayor of Cleveland and the CEO of the Cleveland Metropolitan School District (CMSD) have said that they need to raise the achievement of students in the district big-time. They have crafted a plan to do just that. Cleveland’s charters as a group are no better than their peers in CMSD. If the goal is high quality education for all kids—education at least comparable to what kids in the suburbs are receiving—then Cleveland’s charter sector has as much work to do as does CMSD.
 The z-score calculation is (proficiency rate of building x – average proficiency rate) ÷ standard deviation. Z-scores are in standard deviation units and assume a normal distribution (bell-shaped curve). The shape of the curve is determined by the standard deviation.