Just 1 in 5 adolescents get nine hours of sleep on school nights, and 45% sleep less than eight hours, according to a 2006 poll by the National Sleep Foundation.

Insufficient sleep for teens can lead to a host of health problems, such as increased risk for obesity, stroke and type 2 diabetes.  Lack of sleep can also affect school performance.

Multiple factors, including biological changes in sleep associated with lifestyle choices, and academic demands, negatively impact teens ability to get enough sleep, and pushing back school start times is key to helping them achieve optimal levels of sleep--8 and a half to 9 and a half hours a night, says the American Academy of Pediatrics.

According to U.S. Department of Education, about 43% of the more than 18,000 U.S. public high schools have a start time before 8 a.m.; 15%  8:30 a.m. or later.