Shortening the school week is a controversial policy with little empirical investigation. We examine how shortening the school week can affect the time allocation of children and their parents. In South Korea, the government shortened the school week from 5.5 to 5 days gradually from 2006 to 2011. Using time-use data from 2004-2014, we found that, on Saturdays without school, children spent about half of the extra time freed from school sleeping. Parents reduced hours worked in the labor market and stayed at home with children. Shortening the school week could worsen the intergenerational transmission of inequality.