When parents ask how to give their children the best chance at school success, many teachers suggest something that may not seem particularly “academic”: a good night’s rest. Learning to read, write, multiply, or anything else is hard enough without the added burden of exhaustion.

Now a new study shows that lack of sleep can cause more than just sluggish brains: sleep deprived students are at higher risk of developing the behavioral symptoms of attention deficit hyperactivity disorder (ADHD).

The study, from a team of researchers at the University of Helsinki, Finland, monitored the sleep patterns of several hundred children using small wrist devices called actigraphs. They found that perfectly healthy 7-8 year-old kids who got less than 7.7 hours per night of sleep had increased behavioral problems—such as aggression, an inability to concentrate, and a lack of focus—all symptoms common in children with ADHD.

While there’s been a lot of research on the sleeping difficulties of children with ADHD, and a lot of research on sleep apnea and the behaviors it can cause, there’s been precious little research on how lack of sleep affects previously healthy children, says E. Juulia Paavonen, M.D., Ph.D., who led the study. Paavonen, who did her thesis on children’s sleep difficulties, looked at the increasing rate of ADHD and the fact that today’s children are getting significantly less sleep than children did a generation ago. She had a hunch the two might be connected.

According to the National Sleep Foundation, more than two-thirds of children experience sleep problems at least a few nights each week. Some children have difficulty falling asleep, others staying asleep. The result? School aged children average only 9.5 hours of sleep per night, instead of the 10-11 hours experts recommend. Preschoolers average 10.4 hours, even though it’s recommended that they sleep as much as 2 ½ hours more each night. These may not seem like huge numbers. But research from preeminent child sleep expert Avi Sadeh, of Tel Aviv University, found that getting just one hour less of sleep each night affects student performance by a whopping two grade levels. In other words, a sleepy third-grader will perform at the level of a first-grader.

This is a huge problem, considering how many of our nation’s children are sleepy. American children are increasingly over stimulated and overscheduled. They get an average of one hour less sleep than they did just 30 years ago. When adults are tired, they tend to act groggy and sluggish. But when children are tired, they tend to do the opposite—instead of slowing down, they speed up.

“Lack of sleep does not cause ADHD,” says Lele Diamond, MFT, a child development specialist with an extensive background treating children with behavioral and emotional problems. But she says that lack of sleep can cause behavior that is virtually indistinguishable from it. “Not getting adequate sleep can cause many symptoms such as lack of impulse control, irritability, low frustration tolerance, and difficulty regulating emotions. Needless to say, there’s a strong correlation between all of these effects and poor school performance.”

Although most parents recognize the importance of sleep, getting their kids to go to bed and stay there is another matter entirely. Between bedtime power struggles, nightmares and night-wakings, and intricate sleep stalling tactics, many parents are exhausted by the process of putting their resistant kids to bed each night. Other kids go to sleep without a murmur. Is it nature at work, or nurture?

A little of both, says Noelle Cochran, PsyD, a clinical psychologist and child sleep specialist who works with Diamond. A child’s ability to fall and stay asleep is largely determined by temperament, but the environment parents set as well as the genes they contribute play a part. At the heart of success, Cochran says, is consistency. “The existence of appropriately clear boundaries will aggravate or improve upon a child’s natural proclivities,” she says, “Kids bring their biology and parents either support or undermine what’s already there.”

There are very few kids who need less than the average amount of sleep, experts say. Some kids naturally will get the sleep they need, but others will struggle to get what they need. “When a child is getting less than the average, as a parent you want to do everything you can to increase the amount of sleep your child is getting before it becomes a long-term issue,” Diamond says.

Ready to put your foot down and get your kids on the road to sleep success? Diamond and Cochran have built their careers on teaching parents across the country how to do just that. Here are their tips:

  • Acknowledge the Problem: If bedtime is feeling bad for parents, it’s feeling bad for kids, too. Own up to the issue. Tell your kids you don’t look forward to putting them to bed each night and talk honestly about why.
  • Bring Fears into Broad Daylight: Parents often shy away from talking about fears during the day because they’re worried that will make them worse. If your child seems disturbed by a movie or a TV show, talk about it during the daytime, before bedtime rolls around.
  • Put Magic to Work: Nightmares or fears are very common for kids in preschool or kindergarten because they are right in the thick of the developmental stage of magical thinking. “A big broad imagination is something we want kids to hang onto,” Diamond says, “But when children tell their parents their fears at night, often parents dismiss them with something like, ‘That’s silly. Your lampshade will not turn into the Boogie Man.’ A magical fear needs a magical solution. Tell your child you’re going to “spread mommy love around the room so the monster can’t enter”, or come up with a special face your child can make so the monster can’t come out of the closet. Spray a special “monster spray” around the room.
  • Empower Your Child: Give your child the tools to combat his fears when you are not in the room. A flashlight he can squeeze when he wakes up in the middle of the night gives a child the autonomy he needs to solve problems by himself. It also encourages a child to realize he can take care of himself without waking you up.
  • Outline Expectations, But Keep Them Bite-Sized: Small steps one at a time are better than a strategy that overreaches a child’s ability. Set very clear rules, but don’t be drastic, Cochran says. “For example, if you have a child that keeps getting up at night, start by telling them that their job is to stay in bed for a very small period of time. Then no matter how ridiculously and desperately short, get in there before your child gets out of bed”. Tell your child how great it is that they’re still under the covers, and then set another timeframe, for example, “I’m going to go wash my face and then I’ll check on you again.”
  • Don’t Mess with the Routine: One of the most essential parts of establishing good sleep habits for children is establishing a consistent bedtime routine—then doing everything exactly the same each night. Once you have the routine, don’t alter it. “Never take away part of the bedtime routine, even if your child is acting up,” Diamond says, “Take away something else.” Anxiety is a big reason for preschool and kindergarten sleep issues. If you take away a stuffed animal or other toy during the day as a consequence for bad behavior, make sure you always give it back before bedtime. “You don’t have to give your child time to play with it. Just put it in the room and tell her it will be waiting for her when she gets up in the morning,” she says.
  • Let Kids Know Who’s In Charge: It’s common for kids to test the limits of their power and bedtime is primetime for this. “If children realize they’ve got the power, they will engage parents in a struggle over this power every night,” Cochran says. Often though, kids who challenge authority at bedtime do it throughout the day as well. “Creating an atmosphere where kids experience consistently enforced boundaries throughout the day will help bedtime issues, and vice versa,” she says. Parents need to get back into the position of authority, but also develop a plan with their kids so that it feels collaborative, and not like something that’s being imposed on them, which almost guarantees resistance. “At this age you want kids to feel like they have influence in the process, but not control over the process.”
  • Stick to It: Things can feel worse before they get better, Cochran says. Expect a testing stage. For a quickly adapting kid, changing the sleep routine might take two or three days. For a slow adapting kid, it could be three weeks. “Parents will try for three days and quit, try something else and quit,” she says, “They’ll say nothing works, but they may just have a slow adapter. Those children will adapt. It just takes them longer.” It requires a tremendous amount of consistency. Don’t dabble in sleep training. It can make things worse.
  • Realize Sleep Takes Practice: Self-soothing, the skill that’s needed in order to become a “good” sleeper, is a learned skill. But just because a child may need more help in learning these things, doesn’t mean he will necessarily struggle more in maintaining them once they’re in place. Many parents feel that if they miss the window on sleep training when their child is an infant, it’s all over, but sometimes it’s easier to change the sleep habits of an older child, because you can bring them into the process. You can talk to them about how lack of sleep is affecting their school performance, their self-esteem, their learning, and their friendships. You can help them understand that they have the power to do something about it.

Changing a child’s sleep habits will not happen overnight. But it’s worth the effort; especially since as little as just one hour of extra sleep each night can have a profound affect on a child’s behavior.

“Sleep is highly undervalued in today’s society, and it may be considered a ‘waste of time’” Paavonen says, “particularly among children who have the constant enthusiasm to explore the world. But in fact, sleep promotes well-being, learning, social relationships and development in many, many ways. It’s the cheapest and maybe also the easiest investment that parents can make towards their child’s healthy development.”