After a week back at school, were the kids tired and cranky all week? It may be because they're not getting enough sleep. Dr. Kevin Smith, a sleep specialist with Children's Mercy Hospitals and Clinics, says inadequate sleep can lead to irritability and impaired focus. He suggests children ages 5 to 12 need 10 to 11 hours of sleep. While older students need about nine, Smith says with the increasing demands of homework, sports and extracurricular activities on a student's time, the lack of sleep can also lead to other behavioral problems and can impact a child's ability to learn in school. He adds exposure to light late in the evening can delay our body's ability to fall asleep. Have kids come inside earlier, Smith says, and decrease their exposure to bright lights and light from the screens of electronics such as television, cell phone, and the computer 30 to 60 minutes before bedtime.