Too many teenagers are damaging their health by not getting enough sleep and by falling asleep with electrical gadgets on, researchers say.

A third of 12 to 16-year-olds asked slept for between four to seven hours a night. Experts recommend eight hours.

The Sleep Council, which conducted the poll of 1,000 teenagers, says gadgets in bedrooms such as computers and TVs are fueling poor quality “junk sleep”.

In fact, many experts recommend even more sleep: about 9 and 1/4 hours for a teen. And all seem to agree that removing TVs, computers, phones, and other gadgets is a critical first step.

According to behavioral experts, adolescents generally need eight to nine hours’ sleep each night, beginning around 11 p.m., when most start feeling drowsy. Ideally, then, most students wouldn’t awaken until about 7:30 a.m — about the time most on Long Island are expected to arrive at first-period classes.

There’s a body of research on the impact of sleep and learning. Still, there is resistance to change and concerns about the impact of shifting schedules: “Sixty-five percent of students favored keeping the bell schedule the way it is. Many predicted that a change would make it more difficult to hold after-school jobs, or to participate in clubs and sports.”

Your child may not (yet) be doing all-nighters, but the study “suggests that just as sleep is important for consolidating new memories after they’re learned, as other studies have shown, it’s equally important for preparing the brain to learn new things the following day.”