When children stay up late, they have more academic and attention problems at school, according to a new study from Brown Medical School.

Researchers found children who got eight hours of sleep or less a night were more forgetful, had the most problems paying attention and the most trouble learning new lessons.

"These findings have implications for how we understand attention problems in kids," said lead author Gahan Fallone.

"The children in our study were functioning well at school prior to the restricted sleep schedule. It's likely that other kids who are physiologically or psychologically at risk for learning or attention problems could be even more vulnerable to the negative effects of inadequate sleep."

In the study, 74 healthy, academically successful children between the ages of 6 and 12 were monitored for a three-week period.

During the first week of the study, they slept their normal amount (9.5 hours on average). For the second two weeks, they went to bed a little earlier one week and much later than normal the other.

Teachers rated their academic performance and behavior at the end of each week.

Results showed significantly lower ratings for academic performance and attention during the week that they slept fewer hours, despite the fact that teachers were not told which sleep schedule the kids were on.

The findings are published in the journal Sleep.