High school students who catch up on sleep over the weekend do worse on attention tests in school than kids who don't get extra shuteye, according to a new study from South Korea.

Researchers say the findings suggest "sleep debt" accumulated during the week might be taxing the teens' intellectual resources.

"It's like a bank -- they are on constant, huge sleep overdraft," Dr. David Gozal, an expert in childhood sleep problems at the University of Chicago, told Reuters Health.

"If this is the way you manage your credit card, you will be bankrupt very soon," Gozal, who was not part of the study, said.

On average, the Korean teens -- some 2,600 high school students -- only got five hours and 42 minutes of sleep on weekdays. During the weekend, however, they added nearly three hours of shuteye per night, based on questionnaires.

Those who slept more on weekends -- indicating they were sleep deprived during the week -- did worse on computerized attention tasks in class, Dr. Seog Ju Kim of Gachon University of Medicine and Science in Incheon and colleagues found.

Although their results don't prove that lack of sleep is to blame, they could not be explained by differences in age, sex, depression or snoring, the researchers report in the Archives of Pediatrics & Adolescent Medicine.

Attention problems were not tied to the number of hours teens slept during the week, however. Gozal said that makes sense because some children may thrive on little sleep, whereas those who don't will try to catch up on their sleep debt over the weekend.

To Gozal, the findings are just one more piece of evidence showing that cutting back on sleep can take a toll on youngsters -- even if they're spending the extra waking hours doing homework.

"Attention and executive function is the first step of academic success," he said. "There is enough evidence from animals that shows the need for sleep is not something we can circumvent."

Gozal explained that while Korean students might be getting less sleep than their American peers, sleep has also become a scarce commodity in the U.S. -- among teenagers, adults and even babies.

According to the National Heart, Lung and Blood Institute, school-age children and adolescents should sleep at least nine hours per night, although some do fine on less.

"In a society that is very driven by academic performance," Gozal said, "a child or adolescent that needs to catch up on sleep during the weekend is probably a child at risk."

SOURCE: Archives of Pediatrics & Adolescent Medicine, September 5, 2011.