Students who watch television, movies and video games on school nights do worse in the classroom than peers who don't, a U.S. study has found.

The study of school performance and "screen time" spent viewing television shows, movies — including R-rated content — and video games found that school performance declined as the amount of time spent in front of a screen on weeknights increased.

"Our data support the recommendation that parents limit weekday television and video game time to less than one hour and restrict access to adult media by limiting exposure to cable movie channels and R-rated movies and videos," wrote the study's author, Dr. Iman Sharif of Albert Einstein College of Medicine in New York.

Time spent on the weekend watching television or movies or playing video games did not seem to have an effect on school performance, Sharif reported.

The study, published in Pediatrics, the journal of the American Academy of Pediatrics, found that among the 4,508 students in Grades 5-8 who participated, 36 per cent reported excellent school performance, 38 per cent reported good performance, 20 per cent said they were average performers, and 7 per cent said they performed below average.

The number of students who had poor performance rose as weekday television screen time surpassed three hours and time spent playing video games rose past one hour on weekdays, found the study.

The ratio of students with excellent performance fell from 50 per cent for those who watched no television on weekdays, to 24 per cent for those who had four to seven hours of screen time on weekdays.

'No surprise'

No one should be surprised at the results of the study, says Ben Sawyer.

Sawyer is a co-founder of the Serious Games Initiative, which tries to find ways in which video games can be used in learning and health.

"The bottom line of the study, basically, is that kids aren't doing their homework," Sawyer told CBC. "It's not earth-shattering."

"When I was in high school, my teacher told me the worst thing you can ever do is take a job. He said he would have banned after-school jobs if he could, because there was no way you can do a three-hour job and do two hours of homework after that," he said.

The point, he said, is that anything that takes time away from homework will be reflected in a student's success at school.

"There's nothing wrong with the study saying to parents, 'Beware if your kids aren't doing their homework,' " said Sawyer, who is based in Portland, Maine. "But what I would like to see from these studies is a more nuanced look at the world.

"These studies look at the endpoint of the question. They should be looking at the starting point and trying to figure out what strategies work to get parents involved with their kids and get them excited about learning.

"Homework can be fun for a kid. It's not fun in college."

Video games motivate learning: U.K. study

Another study released on Monday may support Sawyer's point of view.

The U.K. study found that among primary and secondary school teachers and students surveyed, the majority said video games in the classroom helped motivate learning.

The Teaching with Games report, commissioned by video games giant Electronic Arts (EA) and conducted by non-profit research organization Futurelab, surveyed 924 teachers and 2,334 students between the ages of 11 and 16.

It found that 59 per cent of teachers would consider using off-the-shelf games in the classroom, and 62 per cent of students thought using games at school would help learning.

No magic bullet

"The introduction of games … is unlikely to provide a 'magic bullet' to issues of disengagement and disaffection with learning," the researchers wrote.

"Using games in a meaningful way within lessons depended far more on the effective use of existing teaching skills than it did on the development of any new, game-related skills," the study found.

A key obstacle to integrating games in classes was the gap in experience with games between teachers and students.

The study found that 72 per cent of teachers never play games outside of school, while 82 per cent of children said they played video games at least once in a two-week period.