The Friday File: While school closures for bad weather may hurt student achievement, absenteeism profoundly hurts achievement. Each one-day increase in absenteeism lowers math scores by 5% of a standard deviation! Schools deal with school-wide closures by adding days or speeding up the curriculum, but can’t do so with absenteeism. Rather than experimenting with costly and unproven longer days or longer school years, reduce truancy! It’s low hanging fruit!