New data from the Centers for Disease Control and Prevention confirms what most high school teachers already know: U.S. teens aren’t getting enough sleep.

The American Academy of Sleep Medicine recommends that teens get a little more than nine hours of nightly sleep for optimal health and daytime alertness. But CDC data show that only 31.7 percent of high school students report sleeping at least eight hours on a typical school night. This number is up slightly from 31.4 percent in 2011.

The CDC analyzed data from the 2013 Youth Risk Behavior Surveillance System. Students in grades 9–12 at public and private schools completed the survey.

Clearly, American teens are failing to make the grade when it comes to their sleep. At risk is their classroom performance, health and safety.

Parents need to get involved. Help your teen understand that sleep is as important to their health as nutrition and exercise. You also can work with your local school board to implement a high school start time that allows teens to get the healthy sleep they need.

High school teachers also have a role to play. You can help educate students about the importance of sleep. A free high school curriculum supplement about sleep is available from the National Institutes of Health.

Let’s work together to help teens get more sleep.