teenagers

Many parents have pushed for a later start to the school day for teenagers, with limited success. But parents just got a boost from the nation's pediatricians, who say that making middle and high schoolers start classes before 8:30 a.m. threatens children's' health, safety and academic performance.

If you think that teenagers are becoming weaklings, you're right.

Less than half of youths ages 12 to 15 are even close to being aerobically fit, according to data released Wednesday by the Centers for Disease Control and Prevention.

That's down from 52 percent of youths in 1999 to 2000, the last time this survey was conducted. It measures "adequate" levels of cardiorespiratory fitness, which children need not only for sports but for good health.

And that was true regardless of a child's race and family income.

Teenagers put a lot of stock in what their peers are doing, and parents are forever trying to push back against that influence. But with the advent of social media, hanging out with the wrong crowd can include not just classmates, but teenagers thousands of miles away on Instagram, Snapchat and Facebook.

When it comes to persuading teenagers not to smoke, you have to think short-term, the Food and Drug Administration says.

"While most teens understand the serious health risks associated with tobacco use, they often don't believe the long-term consequences will ever apply to them," FDA Commissioner Margaret Hamburg told reporters Monday before unveiling the agency's first-ever anti-smoking campaign.

Sure, you think, my kid's on a football team. That takes care of his exercise needs, right? Probably not.

"There are these bursts of activity," says Jim Sallis, a professor of family and preventive medicine at the University of California, San Diego. "But if you think about it, one hour of playing football out on the field means that the vast majority of that time is spent standing around waiting for the next play."

Cristina Sevin knows the drill. Her 15-year-old son Isaac's first alarm goes off at 6:05 a.m.

When he sleeps right through it, Mom starts the nudging. But she also has to wake up 16-year-old Lily. She flips on the bedroom lights. "Lily, you gotta get up!"

They have to be out the door before 6:35 a.m. in their Annapolis, Md., neighborhood in order to catch the bus for a 7:17 school start. "I wish I didn't have to be awake right now," says Lily.