Arlington County high schools should start later in the morning beginning in September to improve the learning and health of sleep-deprived teenagers, a committee appointed by the county School Board has recommended.

The committee's report, which indicates significant support for moving high school start times from 7:30 a.m. to 8:30, adds Arlington to a growing list of school districts that have considered a major shift in the high school day.

"We strongly believe that continuation of the early start time for high school students is detrimental to student achievement, health and safety," said the panel of school staff members and county residents. The study group was organized by Peter Bruce, chairman of the School Board's advisory council for instruction.

"The evidence in favor of adjusting the school day to the biological needs of young people is overwhelming," the report continued. Efforts to give teenagers in Fairfax and Montgomery counties an extra hour in bed in the morning have been stymied by the cost and complications of changing school bus schedules. But those districts each have seven times as many students as Arlington, where some School Board members yesterday said they thought a later opening time might work in their county.

"I would like to find a way for us to do this," said School Board Chair Libby Garvey, adding that she expected staff members to review the report and make recommendations early next year.

Board member Elaine S. Furlow said, "I believe strongly that if we pulled together the best ideas of bus drivers and families, along with some good routing software, we could have several options that would not cost additional money." She thought the change could be made in time for September. A survey of 88 Arlington high school students showed 75 percent favoring a later start to the school day. The study also said fears that a later opening would interfere with after-school activities might be misplaced, because there is already a 20- to 60-minute break between the end of school and the beginning of sports and other activities, a window that could be narrowed to allow for a later start time.

The Arlington panel relied heavily on the work of researcher Mary Carskadon, whose studies of youth sleeping patterns have influenced school boards nationwide. In a 1997 report by a National Institutes of Health working group on problem sleepiness, Carskadon said children from 10 to 17 require an average of 9.2 hours of sleep a night but rarely get that much.

Some studies indicate that in addition to needing more sleep, adolescents have biological rhythms that make them crave later go-to-sleep and wake-up times. According to those studies, teenagers forced to rise early find it hard to go to bed any earlier, making it that much more difficult for them to get the sleep they need.

Inadequate sleep not only makes them less alert in class but also puts them at risk of consuming too much caffeine, alcohol and nicotine, Carskadon said.