For teens, being tired is the norm. "It's a pretty normal thing to be tired throughout the day," reports Temitayo Fagbenle, WNYC Radio Rookie, who's been interviewing teens about sleep and what's keeping them up late. And it makes sense. Dr. Shelby Harris, director of the behavioral sleep medicine program at Montefiore Medical Center, explains how teenagers' biology makes them want to stay up later, and yet they have to be at school early. She says that teens are not going to be at their best that early in the morning given their body clocks.