Teenagers need more sleep. They also need more time in school. A national push is now underway to address the first problem, which is encouraging — but the second one is no less important.

The American Academy of Pediatrics announced what a growing body of research has found: Teenagers would benefit from a later start to the school day. Like everything else, a teen’s body clock goes a little haywire during puberty, and the hormone that induces sleep (melatonin) is typically not released until about 11 p.m. The glow from electronic devices can delay the release still further — one reason reading a history textbook may help teens fall asleep better than playing “Candy Crush.”

Research shows that the typical teen needs 8.5 to 9.5 hours of sleep to function normally. A 2006 survey by the National Sleep Foundation found that 87 percent of high school students were getting less than that. A big reason is the school day: More than 40 percent of U.S. public high schools start their day before 8 a.m., with 10 percent starting before 7:30.

There’s much more at stake here than reducing the number of yawns in first-period social studies class. When adolescents are sleep-deprived, the consequences can be serious: an increased risk not just for auto accidents and poor performance on tests, but also for weight gain and depression.

The pediatrics academy recommends starting high school no earlier than 8:30 a.m. That’s easier said than done. Later start times can require more money for busing. Many parents like to get the kids out of the house when they leave for work, which is often before 8. And many teachers — who don’t have the same sleeping schedules as their students — prefer an early start and the early dismissal that comes with it. Nevertheless, schools exist to serve students, and the health benefits of later start times are clear. Objections about logistics or finances don’t negate the science.

Allowing students to arrive at school later is not the only scheduling change that would improve academic achievement. In the mid-19th century, urban schools typically ran year-round, with about 250 school days, compared with today’s standard of 180. The 10-week summer vacation came to be largely because school buildings were considered unsanitary during the hot summer months and elites feared too much time in the classroom would create a nation of pointy-headed weaklings incapable of performing the hard labor necessary to make America great.

As U.S. Secretary of Education Arne Duncan said five years ago: “Our school day is too short. Our school week is too short. Our school year is too short.” Some schools that have experimented with longer school days, weekend classes and a slightly longer school year have seen impressive results, as have schools that have delayed their start time. But change has been slow. And some districts are moving in the opposite direction, shortening their days and starting them sooner.

Students need 40 winks a night and more than 40 weeks of school. It shouldn’t be so hard to make sure they get both.

The Hour of Norwalk (Conn.),

Aug. 27