School districts across the country are flipping school start times, making younger students start earlier so teenagers can sleep longer. They cite research, including by the American Academy of Pediatrics in 2014, saying teenagers should start school no earlier than 8:30 a.m.

The moves are creating huge transportation and logistical challenges for school districts, which have to stagger arrival times to deploy limited bus fleets. It’s also causing upheaval at home. In some households, the change pits outraged younger kids against well-rested older ones. Parents remain sleep-deprived.

Some studies say sleep-deprived teens have higher obesity rates, more absences, are at risk for drowsy driving and have attention problems that can hurt learning. Some advocates predict higher test scores and better academic performance from the moves, although the research is mixed.

Get the full story at wsj.com.