Now that school has started, many parents find themselves struggling to shift their kids back to a working routine. As they shave off time for TV and the Internet to make way for schoolwork, parents may want to add extra for that other big contributor to success at school: sleep. Recent research on kids has connected the importance of sleep not only to cognition, but to behavior and mood as well.

While much is unknown about how the brain develops, some researchers theorize that the REM, or rapid eye movement, phase of sleep is when the brain produces and consolidates neural networks for memory and cognition. It's a kind of "formatting of the brain," says Ralph Downey, chief of sleep medicine at Loma Linda University and Children's Hospital in Southern California and a spokesperson for the American Academy of Sleep Medicine. Before the age of 6, a typical child will require between 12 and 13 hours of sleep per night, says Judith Owens, associate professor of pediatrics at Brown University and a noted expert on childhood sleep disorders. At age 6, 10 to 11 hours are needed. While the amount of sleep necessary drops once kids reach adolescence, Owens notes, "they still need at least nine hours under ideal circumstances."

What if they come up short? A sleep-deprived child's reaction is often different from the low energy and sleepiness experienced by adults. "Reducing the amount of hours a child sleeps manifests itself in the child becoming wired and hyperexcitable—exhibiting behavior similar to children with attention deficit disorder," says David Gozal, director of the pediatric sleep program at the University of Louisville in Kentucky. Kids' emotions may become erratic, says Gozal, and they may be less apt to listen or pay attention. Researchers at the University of Montreal report that a study of young children showed that those who slept significantly fewer hours than the recommended 10 were more hyperactive and impulsive than those who got plenty of shuteye and scored lower on two cognitive skills tests. That doesn't bode well for harmony with the teacher.

"Our results indicate that a modest but chronic reduction of just one hour of sleep nightly in early childhood can affect the child's cognitive performance at school entry," says Dominique Petit, a sleep researcher and coauthor of the study. She thinks there's a critical period in early childhood when the lack of sleep is particularly detrimental to development, even if sleep habits improve later on.

But moving "lights out" earlier can be a big challenge. Mark Goetting, a sleep medicine specialist and medical director of the Sleep Health Center in Portage, Mich., offers some recommendations:

Create positive associations with going to bed. "Often, parents will say to a child, 'You can stay up as long as you're good,' or, 'If you don't do what I say, you're going to bed.' It's not healthy to associate going to bed with punishment," says Goetting. "Parents and children will begin to see bedtime as a power struggle." And, of course, both want to win.

Establish a wind-down period before bed. A routine (like reading stories) can let a child know that he's headed toward bedtime and can help him slow down.

Construct a bedroom environment that promotes sleep. "A bedroom should not be a terribly stimulating place," says Goetting. So move the televisions, bright lights, and toys.