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Friday, February 17, 2017

Charter academic performance in Minnesota

The Minnesota School Choice Project is a new initiative aimed at providing a clearer picture of Minnesota's charter schools. Find out more here.

The first question anyone asks about charter schools is how they stack up against traditional schools academically. Charters, which have to recruit their students, often sell themselves to parents and communities as beacons of academic opportunity, and much of the political momentum behind charters is rooted in the impression that they can produce pass rates and test scores far above and beyond those seen in traditional district schools.

But in Minnesota, these claims are false, at least on a sector-wide basis.

Previous work suggests that Minnesota traditional schools outperform charter schools in the aggregate, and our latest report shows that this is still the case.

The report uses a regression model to compare pass rates in math and reading between charter and traditional schools. The findings across a number of years can be seen in the table below, in which negative numbers represent lower scores for charters:

Not only are pass rates lower in charters, the gap in scores is relatively steady for both subjects across the entire timespan.

Charter school advocates have responded to these findings by asserting that this isn't really a fair comparison, because students at charter schools are different than students elsewhere. For instance, in response to coverage of our report in the Pioneer Press, long-time charter supporter Joe Nathan responded that "these comparisons fail to account for the types of students charters often serve, including those who were unsuccessful in traditional schools."

This criticism makes no sense in context. The use of a regression model with student demographics controls for all key student characteristics monitored by the state, such as race, income, or special education or English learner status. If charters tended to enroll more students with a lower propensity for academic achievement, the model would show a smaller gap between charters and traditionals, not a larger one. (And as future posts will demonstrate, many Minnesota charters are considerably less likely to enroll students with special academic needs.)

Now, there are also differences between students that don't show up in state data and thus can't be included in the regression model. For instance, some families are simply more academically engaged than others.

But if anything, omitting those differences is likely to help charters, in the aggregate. That's because families whose children attend a charter school have to seek out the school and enroll their child. This creates selection bias: because a baseline level of educational participation is necessary to enroll at a charter, you would expect charter families to be, on the whole, more academically engaged than non-charter families. While measuring the full impact of this selection bias on Minnesota score gaps is all but impossible, it is likely a substantial consideration.

In other words, if you could fully "account for the types of students charters serve," there are very compelling reasons to think the gap between charter and traditional school performance would be larger and even less favorable to charters.

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