With snow expected to pound the mid-Atlantic this weekend, schools are bracing for possible “snow days” on Friday or Monday. Some Washington, D.C.-area schools are even closed Thursday after icy road conditions Wednesday evening. Conventional wisdom says snow days are bad for learning; after all, on snow days, students stay home instead of going to school. But a study published in 2015 by Education Next says otherwise.

When there is moderate snowfall, student absences rise significantly while few schools close, according to research by Joshua Goodman with Harvard University. This can cause teachers problems, because they may have to split their time the following day between students who did and did not attend school the prior day. “When a few students miss a day or more of instruction, the teacher can review the recently presented material for those students who missed it, in which case the absent students’ peers lose out on valuable instructional time, or she may move forward with new material and risk having the absent students fall behind,” Goodman writes.