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Why keeping school open in the snow can make test scores go down

A child in the snow in Washington, DC.
A child in the snow in Washington, DC.
Chip Somodevilla/Getty Images

It snowed a couple of inches in Washington, DC, this morning, and the roads are (unsurprisingly) atrocious. But school is in session in most of the region's major school districts.

Was this the right call? Research suggests it's better to call off school, even for just a middling amount of snow, according to a working paper published by the National Bureau of Economic Research in June.

That's because teachers are better at making up for lessons missed when the entire class is gone for a snow day than they are at helping students catch up on what they missed from an ordinary absence. And when it snows, many kids don't go to school even if it isn't canceled.

Joshua Goodman of Harvard's Kennedy School of Government studied data from Massachusetts weather records and standardized test scores. Moderately snowy days, with 4 to 10 inches of snow, didn't lead to school closures (yes, this is Massachusetts, not the mid-Atlantic), but they did lead to more absences. And absences led to lower test scores. Extremely snowy days, on the other hand, had no effect on achievement — because the entire class was gone at once and could make up a lesson at the same time.

"When students return to school after a snow day, they have all missed exactly the same lesson," he wrote. "Teachers can thus compensate by pushing all of the their lesson plans back a day for the rest of the school year. This will have no effect on student achievement as measured by standardized tests, so long as the teacher's planned schedule had included at least some instructional time devoted to subjects not on the tests."

Of course, giving kids a snow day when businesses and offices are still open is a huge headache for parents, who have to arrange last-minute child care or try to work from home. But from a test score perspective, it suggests canceling school is the right call.