A recent study finds that adding even a small additional period of sleep to kids’ schedules could yield significant benefits to everything from behavior to academic performance. If, instead, the time the kids are allowed to sleep is reduced, kids will exhibit behavior problems, mood swings and will be unable to pay attention in class.

The study, published in this month’s Pediatrics journal, looked at the sleeping habits of 33 children between the ages of 7 and 11. During the first week of the two-week experiment, researchers found that the children got an average of 9.3 hours of sleep — less than the 10 hours a night recommended for kids at that stage of development. During the second week, the children were split into two groups, with one gaining an hour of sleep per night and the other losing an hour. Parents were unable to add a whole hour, so the first group only gained an additional 30 minutes of sleep per night.

Still, that half hour seemed long enough for teachers to notice an improvement in the kids’ behavior.

After the first week of monitoring, the teachers answered questions that rated the children’s emotions, moodiness and restlessness at school on a scale from zero to 100, with higher scores indicating worse behavior and scores above 60 signaling a behavioral problem.

The baseline score for both groups of kids before the sleep manipulation began was about 50.

The teachers were asked to reevaluate the students after the second week without knowing which kid fell into each experimental group. The results were telling. Students who got an extra half an hour of shut-eye improved to a score of 47, on average, while those who lost an hour of sleep had more behavioral problems and had an average score of 54. Although the differences weren’t large, Reut Gruber of McGill University and Douglas Research Center, the lead author of the study, said that they were still significant enough for the teachers to notice.

The parents noticed, too. Those whose children had extra sleep reported their kids as being less tired and cranky during the course of the day and at night. The impression of parents whose children lost sleep were exactly opposite.

“The thing that was surprising was how little sleep extension could affect functioning on a day-to-day basis,” said Dr. Umakanth Khatwa, sleep lab director at Boston Children’s Hospital in Massachusetts, who was not involved with the new study.

Gruber told Reuters Health that while the study only included 33 kids, it was still able to show more sleep leads to better behavior.