After a summer of vacations and late nights, it's time to set those back-to-school alarms. A good night’s sleep helps students stay focused and attentive in class. Experts say it's worth easing kids back into a routine with the start of a new school year. “We don't say ‘get good sleep’ just because,” said pediatrician Dr. Gabrina Dixon with Children's National Hospital. “It really helps kids learn and it helps them function throughout the day.” The amount of sleep kids need changes as they age. Preschoolers should get up to 13 hours of sleep. Tweens need between nine and 12 hours. Teenagers do best with eight to 10 hours of shut-eye. Set an earlier bedtime Early bedtimes can slip through the cracks over the summer as kids stay up for sleepovers, movie marathons and long plane flights. To get back on track, experts recommend setting earlier bedtimes a week or two before the first day of school or gradually going to bed 15 to 30 minutes earlier each night. Don't eat a heavy meal before bed and avoid TV or screen time two hours before sleep. Instead, work in relaxing activities to slow down like showering and reading a story. “You're trying to take the cognitive load off your mind,” said Dr. Nitun Verma, a spokesperson for the American Academy of Sleep Medicine. “It would be like if you're driving, you're slowly letting go of the gas pedal.” Parents can adjust their back-to-school plans based on what works best for their child. Nikkya Hargrove moves her twin daughters' bedtimes up by 30 minutes the week before school starts. Sometimes, her 10-year-olds will negotiate for a few extra minutes to stay up and read. Hargrove said those conversations are important as her children get older and advocate for themselves. If they stay up too late and don't have the best morning, Hargrove said that can be a learning experience too. “If they're groggy and they don't like how they feel, then they know, ‘OK, I have to go to bed earlier,’” said Hargrove, an author and independent bookstore owner (note to Alicia - may need only one?) from Connecticut. In the morning, soaking in some daylight by sitting at a window or going outside can help train the brain to power up, Verma said. Squash back-to-school sleep anxiety Sleep quality matters just as much as duration. First-day jitters can make it hard to fall asleep no matter how early the bedtime. Dixon says parents can talk to their kids to find out what is making them anxious. Is it the first day at a new school? Is it a fear of making new friends? Then they might try a test run of stressful activities before school starts to make those tasks feel less scary — for example, by visiting the school or meeting classmates at an open house. The weeks leading up can be jam-packed and it's not always possible to prep a routine in advance. But kids will adjust eventually so sleep experts say parents should do what they can. After all, their kids aren't the only ones adjusting to a new routine. “I always say, 'Take a deep breath, it'll be OK,'" Dixon said. “And just start that schedule.”