It’s one of the great parenting dilemmas: How much time should you allow your kids to spend playing video games, surfing the Internet, and watching television? It’s easy to say zero screen time is best, but video and online games and DVDs are so convenient—they keep kids occupied when parents need to focus on a task or, say, make a phone call. They come in handy in the car by making the long ride to the soccer game seem not quite so long. And some games and shows even seem to help children learn to read and do math.

Is it OK to lean on quality, age-appropriate electronic games and TV programs just a little bit? Or does doing so put kids at risk for aggressive behavior, difficulty paying attention in school, and a preference for indoor, electronic entertainment over outdoor play?

Douglas Gentile, an associate professor of developmental psychology at Iowa State University, has extensively studied the effects of television and video games on children. Surprisingly, he says children can actually benefit from educational TV shows and computer games.

“Educational TV is fantastically good for kids,” Gentile says. “Kids who watch Sesame Street as kids are still getting better grades in high school.”

Parents need to consider what types of television and games kids engage with and how much time they spend in front of a screen. “What my research has taught me is that media are far more powerful than we thought them to be,” Gentile says. “The negatives and positives are both greater.”

It’s About Quantity

The American Academy of Pediatrics recommends that children younger than age 3 shouldn’t watch any television or play computer or video games. For elementary school kids, one hour per day is the maximum, and for middle schoolers, two hours per day is the recommended limit.

There’s an exception, however: “If you’re using the computer for schoolwork, it’s OK,” Gentile says. “That’s free.”

In addition to time limits, the AAP advises against letting kids have televisions and computers in their bedrooms. Research shows that children who spend too much time in front of a screen have an increased risk of obesity and addiction.

In a study he coauthored in 2010, Gentile found that children who are exposed to more than two hours of screen time per day are more likely to have trouble concentrating in school. The constant flickering lights, changes in imagery, and instant gratification may train kids’ brains to always expect that level of stimulation, making it harder for children to focus in a classroom, he says.

Many parents find the AAP guidelines too lenient. Others, however, think their kids are within the guidelines when, in reality, they are way over the time limits and watching too much. “Parents aren’t all that good at judging the time our kids spend in front of a screen,” Gentile says. “We get sidetracked. Our kids don’t do all their viewing in one sitting. The total time is often more than we imagine.”

But there is help: Gentile has a workable strategy for managing screen time. “Set up a token economy, with chips or bills,” he says. If you want your child to limit his screen time to 10 hours a week, you can give him 20 tokens (or coupons worth 30 minutes each). He can buy his TV time one coupon at a time, or he can use several coupons to spend a Saturday afternoon playing his favorite computer game. “It works like an allowance,” Gentile says. “An allowance teaches kids to budget their money, and this teaches kids to plan their screen time.”

When children are aware of how much time they have, they are more likely to spend it watching shows and playing games they enjoy rather than watching television out of boredom. This method is effective because it gives kids choices and curbs arguments and power struggles.

Parents can also use online tools and external devices to monitor and control the time their children spend online. “It puts the control in the hands of the parents,” Gentile says. “When time’s up, it’s off.”

It’s About Quality

Research has shown clear connections between screen time and aggression in kids, according to the AAP.

In a 1999 policy statement on media education issued by the AAP’s Committee on Public Education, the committee wrote that “More than 1,000 scientific studies and reviews conclude that significant exposure to media violence increases the risk of aggressive behavior in certain children and adolescents, desensitizes them to violence, and makes them believe that the world is a ‘meaner and scarier’ place than it is.”

“It’s not just gory and realistic violence that impacts kids,” Gentile says, adding, “What matters is whether you practice intentional harm to something. Even cute, cartoonish games can have the same effects of bringing out aggression in kids.”

The wildly popular game Angry Birds is on the low end of the violence spectrum, Gentile says. He notes that the biggest question for parents to consider is whether players are rewarded for harming other characters.

Some games reward children for making positive decisions. Animal Crossing, for example, encourages helpfulness, Gentile says.

Games like Reader Rabbit and Math Blaster can help students learn—without them knowing it. “These games teach kids in a way that kids don’t realize they’re learning,” Gentile says. “They provide practice.” On public television, many shows combine education and entertainment, helping children learn basic skills and positive character traits. “These shows are worth spending time with,” he says.

Some children’s shows and games are neither harmful nor educational, and Gentile thinks that’s OK in moderation. “There is nothing wrong with being entertained,” he says. “With a game like Angry Birds, the content is not likely to be the issue, but the time spent with it, and therefore not with something more beneficial, is more likely to be what parents should consider.”

Journalist Patti Ghezzi covered education and schools for 10 years for the Atlanta Journal-Constitution. She lives in Avondale Estates, Ga., with her family, which includes husband Jason, daughter Celia, and geriatric mutt Albany.