More than two thirds (69 percent) of high school students get less than 7 hours of sleep on an average school night, reports the CDC, which considers less than 7 hours insufficient. Here is the percentage by grade...
Percent who get less than 7 hours of sleep on average school night
9th graders: 60%
10th graders: 67%
11th graders: 73%
12th graders: 77%
Source: CDC, Sleep Duration and Injury-Related Risk Behaviors Among High School Students—United States, 2007-2013