It’s time to bury what you think you know about snow days and student achievement.

Joshua Goodman, an assistant professor at Harvard’s Kennedy School of Government, examined weather data, student test scores and attendance figures in Massachusetts between 2003 and 2010. He found that school closures on snow days do not hurt student progress.

But individual absences driven by bad weather? Those do end up taking a toll, especially on children’s math performance, according to Goodman’s research.

The idea that snow days would have less of an impact than absences makes some sense given the graph below, which shows how children — especially poor children — tend to miss far more instructional time because they miss class than they do because school is closed. Goodman argues that the results suggest that schools should get busy figuring out how to improve student attendance and how to make sure that teachers have the tools they need to help absent children catch up without slowing down the rest of the class.

Goodman’s research paper, “In Defense of Snow Days,” was published online Thursday and will appear in the summer 2015 issue of Education Next, a journal published by the Hoover Institution.