Many districts are reluctant to change their schedules because they see the shift as too expensive and disruptive, but that’s short-sighted, says an op-ed writer to the Los Angeles Times.

Later start times can mean less missed school — absences dropped 15% in Bonneville County, Idaho, after it instituted such a change, according to a 2014 Children’s National Medical Center report. In states such as California where state funding for schools is tied to attendance, it follows that later start times could translate into extra dollars. Megan Reilly, chief financial officer for the Los Angeles Unified School District, has estimated that boosting attendance by just 1% districtwide would bring in an additional $40 million per year.

Repeated studies also show that when the school day starts later and teens get more sleep, both grades and standardized test scores go up. A Colby College economist, Finley Edwards, found that a one-hour delay in start time increased math test and reading test scores by three percentile points. Even more striking, the lowest-scoring students showed the biggest jumps.