"Getting back on a normal sleep schedule doesn't just happen overnight," Peter Bidey, instructor of family medicine at Philadelphia College of Osteopathic Medicine, said in a college news release.
"A gradual transition back to regular sleep habits is essential. A drastic change in sleep habits can be a shock to your child's system," he explained.
During summer vacation, children tend to stay up later and sleep in longer. Letting them continue that pattern until school starts can lead to trouble that first morning they have to wake up early for class, Bidey pointed out.
Getting children back into a sleep schedule for school "should start at least a week before school begins," Bidey said. "Parents can begin waking their children up earlier each day with an alarm clock, and sending their child to bed a bit earlier each night."
One way to make mornings before school less hectic is to be well-organized, he suggested.
"Parents can pack lunches and lay out school clothes the night before. That will help them stay calm in the mornings, which will in turn keep children calm," Bidey said.
Research shows that adequate sleep benefits children's mental health and school performance, he noted.
The National Sleep Foundation has more about children and sleep.