Research on the societal costs of disaster‐related US school closures has focused, and due to COVID‐19 will likely continue to focus, on pandemics, with very limited research on closures from natural hazards. This is surprising given that school closures occur frequently to protect children, teachers, and staff pre‐event as well as post‐disaster to convert facilities into emergency shelters, etc. This study investigates the secondary effects from post‐flooding, temporary school closures after the catastrophic 2015 flash flood in Richland County, South Carolina. Lost productivity from school closures was quantified using the Human Capital Method. Out of the 208 completed surveys, 75% of households had children that missed school. Post‐stratifying survey results on race produced an average of $437 in lost productivity due to school closures and an overall $2175 in lost productivity due to flood‐related impacts in general. Expressed in FEMA benefit‐cost analysis terms, our study shows that schools have a standard value of $215 per household and per day for the unweighted sample ($180 for the race‐weighted sample). Furthermore, households' disutility for a late start is almost as great as their disutility for a school closure. These exploratory findings suggest that unplanned school closures should be minimized, and community characteristics carefully considered to avoid unintended socioeconomic consequences.