Science says teens need more sleep. So why is it so hard to start school later?

The science is clear that teens can benefit from later school start times, but in Nashville and other communities, it's politically difficult to make the change. (PeopleImages/Getty Images)

NASHVILLE, Tenn. — High school classes start so early around this city that some kids get on buses at 5:30 in the morning.

Just 10% of public schools nationwide start before 7:30 a.m., according to federal statistics. But in Nashville, classes start at 7:05 — a fact the new mayor, Freddie O'Connell, has been criticizing for years.