More than 90 percent of Fairfax County students are sleeping less than the recommended nine hours, a survey co-sponsored by the county government and school board found.

The deficit was biggest in high school: 56 percent of eighth-graders said they slept at least eight hours a night, but only 17.3 percent of 12th-graders said the same. One-third of seniors said they logged just six hours each night, and nearly one in 10 students reported sleeping four or fewer hours.