Using Admissions Lotteries to Validate and Improve School Quality Measures

Blueprint Labs:

Parents increasingly rely on data-driven measures of school quality to choose schools, while districts use the same information to guide policy. School quality information often comes in the form of “school report cards” like New York City’s School Quality Snapshot and “school finder” websites, like GreatSchools.org. These school ratings are highly consequential, influencing family enrollment decisions and home prices around the country. State and district restructuring decisions, such as school closures or mergers, also turn on these measures. In short, school performance measures matter.

Our study examines the predictive validity of alternative school performance measures to show how they can be improved in districts that use centralized assignment to match students to schools. Using data from New York City and Denver, we show that a new approach that harnesses student data from centralized assignment, which we call a risk controlled value-added model (RC VAM), improves upon conventional methods. We also study a range of other value-added models. In practice, analysts may not have the data required to compute RC VAM and not all districts assign seats centrally. Our study sheds light on approaches that might best serve as performance measures in the absence of ideal data.

The validity of school ratings is important to both policymakers and parents, who rely on them for consequential decisions. Inaccurate measures of school quality can unfairly reward or punish schools erroneously deemed to be more or less effective. For organizations that engage in the provision of quality measures, the methods developed in our study offer a new tool that can provide fairer assessments of school effectiveness.


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