By Marc Torrence:

Cranky teenagers aren't the only ones who think school should start later in the morning. Many influential scientists agree with them.

Teenagers who don't get enough sleep are more likely to use drugs and alcohol, be overweight and underperform academically, the Centers for Disease Control and Prevention says. The center recommends at least 8.5 to 9.5 hours of sleep per night, and that schools should start at 8:30 a.m. at the earliest. But that's not exactly happening across America.

Later start times are facing battles from school boards over logistical and financial issues. Fewer than one in five middle and high schools in the United States begin classes later than 8:30, according to a study released Thursday by the CDC that has given supporters of later start times additional ammo for their fight. "Clearly, the decisions are not made based on students' health and safety and academics so much as things like bus schedules and other factors like that," Anne Wheaton, author of the CDC study, told Patch.

The 8:30 start comes from the recommended sleep time for adolescents combined with a pubescent effect as common as pimples, body odor and angst — a change in natural sleep patterns that pushes back what scientists refer to as the circadian rhythm.

"That delay on your internal clock is one of the earliest signs of puberty. It makes it really difficult for the teenager to fall asleep before 11 o'clock," Wheaton said. "If you try to go to bed by 11, and get the adequate amount of sleep, then you push school start times back until 8:30."

In 2014 ,the American Academy of Pediatrics urged schools to adopt start times of 8:30 a.m. at the earliest. Some schools changed right away. Most didn't.