Getting them back on schedule is no easy task, but it doesn't have to be that way.
"I like to stay up late at night and sleep late in the morning," 9-year-old Jessica Mann said. "I'm like nocturnal."
But nocturnal doesn't work very well when school starts and the alarm goes off at 6:45 a.m. Jessica's sister Lauren has some tough advice
"She has to just deal with it," she ssaid. "I have to just deal with it."
If your kids are also night owls in the summer, you're not alone.
"She's probably sleeping the right amount of time, but not at the right time," sleep specialist Dr. Michael Breus said.
He says start the sleep transition early, by having them go to bed and get up 15 minutes earlier each day until school starts.
"We don't want to slam them into a new bedtime," he said. "Gradual will work better."
Limit all caffeine intake after 2:30 p.m. and have a wind-down period before bed, including a warm bath.
And here's a tip for kids and parents. Enforce an electronic curfew - that means 1 hour before bedtime, turn off all the technology.
In a recent survey by the Sleepy's mattress company, 66 percent of parents said their kids use at least one electronic device after bedtime. But studies show that exposure to light disrupts sleep, which will of course make mornings more painful.
And to ease that morning routine, Dr. Breus says go in at night after your kids fall asleep and open up the blinds.
"A lot of natural light comes in that's going to be helpful for her to wake in the morning," he said.
You can also use a clock that simulates a sunrise.
Anther tip is to make sure your kids are really active during the day. That will help them fall asleep earlier while you're trying to make the transition.