Because researchers studying circadian rhythms have discovered that most teenagers are really nocturnal, school administrators should take this into account when organizing a school day. For example, traditionally teenagers must arise in the predawn hours and arrive at school before sunrise. Groggy and unfocused, they find it difficult to concentrate and be alert before lunch. After lunch, which for many students in overcrowded high schools begins at 10:30 a.m., they are finally able to pay attention. Armed with this information, the school board should be innovative and rearrange the schedule, which would curb truancy in grades 8 through 12.