The alarm goes off at 6 a.m. Then it goes off four more times, because an extra 10 minutes of sleep trumps sitting down for breakfast. A granola bar on the bus is the gourmet breakfast of choice. The morning bus arrives at its stop by 6:38 a.m. and rolls into the school’s roundabout by 7 a.m. on the dot. Thirty more minutes blur by before another alarm goes off — the one that tells students it’s time to break out of zombie mode and start learning.

But for teenagers, their brains hit the snooze button for them. Welcome to an early school start time.

The Centers for Disease Control and Prevention recently released a report analyzing the start times of public middle and high schools in the U.S. Results show that only 17.7 percent of schools start classes at 8:30 a.m. or later. About 32 percent start school between 7:30 a.m. and 8 a.m. Nearly 7 percent of schools start before 7:30 a.m.

What’s wrong with an early school start time for teens? The problem is that during puberty a biological change delays the timing of a teen’s body clock. This explains why teens tend to remain alert later at night. As a result, teens have a hard time going to bed early enough to get the 9 hours of sleep they need before waking up for school.

This is bad news for students in a few different ways. Teens who don’t get enough sleep run a higher risk of being overweight. They also are more likely to suffer from depression or perform poorly in school. Sleepy teens also have a higher risk of being involved in a drowsy driving accident. Research suggests that teen car crash rates are higher when school starts earlier in the morning.

The American Academy of Sleep Medicine has a health advisory recommending that parents and school districts work together to implement smarter school start times for teens. But later school start times are only one part of the equation for healthy sleep in teens. The AASM also encourages parents to help teens make sleep a priority. Keep TVs and computers out of your teen’s bedroom, and set a communication curfew on school nights.

The morning routine doesn’t have to be a struggle. Let’s work together to give students the edge they need for a successful high school experience.