Like every good parent, you want your kids to get into the right schools, get the best grades, have the most worthwhile extracurricular activities, and have great careers. So you plan for as much extra help and extra after-school activities as you can.

Unfortunately, that's the wrong approach, according to a policy paper from the American Academy of Pediatrics. That's because to be mentally healthy and successful in work and life, kids need plenty of free time for play. 

"Research demonstrates that developmentally appropriate play with parents and peers is a singular opportunity to promote the social-emotional, cognitive, language, and self-regulation skills that build executive function and a prosocial brain," the researchers write. In other words, they say: "Play is not frivolous: it enhances brain structure and function."

Unfortunately, today's children are getting less and less of it. According to the report, children between the ages of 3 and 11 have lost an average 12 hours a week of free time. A national survey found that only 51 percent of children went outside to walk or play with a parent on a daily basis, and only 58 percent who were not in child care got to go outside daily. And, due to the need for increased academics, 30 percent of U.S. children in kindergarten no longer have recess.

The Academy wants to reverse this trend, and it's calling on pediatricians to advocate with both parents and school systems for "the protection of unstructured playtime because of its numerous benefits."

Just what are those benefits? The report lists numerous studies that demonstrate how it helps with learning, brain function, and physical health. Here are some ways that playing gives children skills they need: 

1. Object play helps children develop abstract thought.

Object play starts in infancy, like when a baby sticks your car keys in her or his mouth. But it evolves as children grow and they learn to use one object to represent another--for example, pretending that a cardboard box is a car or a house. That use of symbolic objects helps with abstract thought, the authors say.

2. Physical play helps children be active team players.

Physical play, which can include things like pillow fights and free play at recess, brings a whole host of benefits. To begin with, "The development of foundational motor skills in childhood is essential to promoting an active lifestyle and the prevention of obesity," the authors write. Rough-and-tumble play, as in a schoolyard, helps children learn to both win and lose graciously, and also allows them to take risks in a relatively safe environment. All this, the authors write, "fosters the acquisition of skills needed for communication, negotiation, and emotional balance and encourages the development of emotional intelligence."

3. Outdoor play helps develop sensory skills. 

The physical and mental health benefits of being outdoors are so well documented that in Japan health insurance companies reimburse people for spending time in the woods, which they call "forest baths." 

Playing outside helps students develop sensory, motor, and cognitive skills. "It is not surprising that countries that offer more recess to young children see greater academic success among the children as they mature," the authors write.

4. Pretend play builds social skills. 

Remember playing house? It always seemed to involve complex negotiations. I'll be the Daddy, you be the Mommy. Or I can be the Mommy, but then I get to wear the hat. And so on. "Play with other children enables them to negotiate 'the rules' and learn to cooperate," the authors write. Social play is when children often learn to take turns, and they develop their language skills as they seek to explain the make-believe world they're envisioning.

More parent time, less screen time.

The report stresses the importance, not only of giving children free time to play, but also of parents (or other caregivers) spending some of that time playing with them. When adults play with children, they often provide what researchers call "scaffolding,"--a little bit of help or a hint when children are stuck on a task that then allows them to complete the task for themselves. Scaffolding is very important for children's development, the report says. "Caregivers are needed to provide the appropriate amount of input and guidance for children to develop optimal skills."

And if you're accustomed to plopping your children in front of the TV, or handing them a phone, tablet, or other device to play with, the report has some bad news for you. Screen time is nowhere near as good for your kids as unstructured playtime, outdoors or indoors, interacting directly with adults and other children. This is true even when the game they're playing or content they're watching is intended to be educational. The report notes: "Researchers have compared preschoolers playing with blocks independently with preschoolers watching Baby Einstein tapes and have shown that the children playing with blocks independently developed better language and cognitive skills than their peers watching videos." Playing video games, especially those where children interact with their peers within the game, can have learning benefits, some research suggests, and the report concedes this may be true. But it still isn't as good as going outside for unstructured play with other children.

Getting your children to put down the TV remote or the video game and go outside and play might be a challenge. Still, for the sake of their future health and success, that's where they should be.