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Study: Class size doesn’t matter

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Two Harvard researchers looked at the factors that actually improve student achievement and those that don’t. In a new paper for the National Bureau of Economic Research, Will Dobbie and Roland Freyer analyzed 35 charter schools, which generally have greater flexibility in terms of school structure and strategy. They found that traditionally emphasized factors such as class size made little difference, compared with some new criteria: Darrin Phegley AP

We find that traditionally collected input measures — class size, per pupil expenditure, the fraction of teachers with no certification, and the fraction of teachers with an advanced degree — are not correlated with school effectiveness. In stark contrast, we show that an index of five policies suggested by over forty years of qualitative research — frequent teacher feedback, the use of data to guide instruction, high-dosage tutoring, increased instructional time, and high expectations — explains approximately 50 percent of the variation in school effectiveness.

“Data-driven instruction” may be the least familiar policy of the bunch. Dobbie and Fryer explain: “We attempt to understand how schools use data through the frequency of interim assessments, whether teachers meet with a school leader to discuss student data, how often teachers receive reports on student results, and how often data from interim assessments are used to adjust tutoring groups, assign remediation, modify instruction, or create individualized student goals.”

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