Would starting school later in the morning improve teenagers' academic performance?

According to recent reports by the National Sleep Foundation and several university research centers, teenagers are wired to be sleepier in the morning -- their levels of melatonin (a sleep-promoting hormone) don't fall until at least 8 A.M. As a result, some high schools have begun delaying the morning bell in order to make the school day more manageable for sleep-deprived teens. Some argue, however, that most of the evidence for teenage sleep patterns remains anecdotal, starting school later would cut into after-school activities, and other factors should take priority when it comes to student achievement.