For-profit schools gain in Philly

Philadelphia students in public schools run by for-profit managers did much better in math (and slightly better in reading) than in district-run schools, concludes a study published in Education Next by Paul Peterson and Matthew Chingos.  Students in schools run by non-profit managers did worse, especially in math.

At schools under for-profit management, students learned on average 25 percent of a standard deviation more in math each year of the six years of the intervention than they would have had the school been under district management. The estimated impact each year was roughly 60 percent of a year’s worth of learning, a large, statistically significant impact. Our adjustment using results from an alternative model that includes the larger number of students yields a positive annual impact of for-profit management on math performance of 12 percent of a standard deviation, 29 percent of a year’s worth of learning.

The estimated average annual impact on reading performance of for-profit management relative to district management is a positive 10 percent of a standard deviation, approximately 36 percent of a year’s worth of reading. However, that impact is not statistically significant. The adjusted impact was just 4 percent of a standard deviation, about 14 percent of a year’s worth of learning.

The school district has taken back control of four schools run by for-profits and one run by a non-profit.  That decision makes little sense, write Peterson and Chingos.

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  1. This feels wrong. 25% of a standard deviation is 60% of a year’s worth of learning? Shall I conclude that one standard deviation is 2.4 years’ worth of learning per year, and conclude thereby that a substantial fraction of students are forgetting more than a year’s worth of material per year? I mean, I have a cynical side that is more than happy to cackle over this prospect, and my statistical background is weak, but my husband’s isn’t and he finds these numbers odd too. Is the thing we’re dealing with here not a normal distribution, in which case “standard deviation” is a misleading term? We are baffled.