(CNN) - It turns out sleepy students make crabby classmates.
According to a new study published in Pediatrics, students who sleep less behave worse.
Researchers looked at 43 students, ages seven to 11, for the study.
For one week, half the kids were put to bed half an hour earlier than usual. The other kids stayed up almost an hour later than normal.
Researchers found the kids who got less sleep were more impulsive and irritable than their rested classmates.
They were quick to cry, lose their tempers or get frustrated.
The children who got plenty of sleep had a better handle on their emotions and were more alert in class.
Experts said elementary school children need 10 to 11 hours of sleep each night.
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