(CNN) -- Fresh air, physical activity and a chance to run around with friends are big draws for the millions of kids who fill football fields, baseball diamonds, soccer pitches and basketball courts across the United States.
And experts say children can also learn some valuable life lessons -- if their parents stay on the sidelines.
"Sports are a wonderful vehicle for kids to learn how to deal with adversity, the sense of learning how to master skills," said Rick Wolff, chairman of the Center for Sports Parenting and a former professional baseball player and coach. "For example, if they're learning how to dribble a basketball first with one hand then with another, [it] gives them a sense of accomplishment."
The National Council of Youth Sports estimates that about 41 million boys and girls play organized sports, and that number has been growing steadily. (Full story)
Wolff, who's also the author of "Coaching Kids for Dummies," said that it's good for kids to learn how to bounce back if they strike out or get cut from a team and to talk to their coach if they don't think they're getting enough playing time.
"If parents really do want their children to enjoy amateur sports -- while it's wonderful to be supportive, as you should be -- it's really about having your child go out and learn life lessons from the actual experience," he said.
Darrell Burnett, a clinical psychologist who specializes in youth sports, said that sports can give kids the building blocks of self-esteem.
"If you plug a little guy or girl into sports ... they automatically get the uniform, the trophy, the snacks and the team name and the nicknames and photos and see each other at school," he said. "All of that is an instant sense of belonging."
Burnett said that recreational leagues that let everybody play, regardless of their ability, make kids feel worthwhile while giving them a sense of self-respect and dignity.
It also gives them some control in a world run by parents and teachers, he said.
"They're going to be learning to use the tools of the trade [of the sport they're playing]. They're going to learn the rules of the game -- and the more they learn, the more they are in control -- and they're going to learn about sportsmanship and [how] to control their emotions," Burnett said.
Kids first, athletes second
Burnett said that it is important for parents to see their children as kids who happen to be good athletes, "because if you don't, the kid runs the risk of his or her self-esteem being tied to performance, which can be tragic."
"I had one girl who went 0-for-4 in softball who said that when she got home, nobody talked to her at supper," he said. "And even more tragically, I had a boy who was a very good athlete. He had a full [scholarship] as a senior. He was going to go to a Division I school in football. He was a big kid, and a big kid on campus. Then he blew out his knee, lost the offer, lost his scholarship and tried to commit suicide."
Burnett said the boy was distraught because he felt he had blown his big chance, and he felt like he had let his parents down.
"Whether the parents proposed that or not, it was the kid's perception," he said. "And if the kid somehow perceives that he's not a kid first, then that becomes a problem."
Burnett said he once saw a 9-year-old whose father brought him in for treatment because he felt the boy wasn't motivated. The boy was on two baseball teams and had practice two or three times a week. But the father was upset because he did not want to hit a ball off of a batting tee 200 times a night to improve his swing.
"It's like parents with really smart kids (who say), 'You'll never get into Stanford this way,' " Burnett said. "Well, the kid's 9, he doesn't even know what Stanford is, and they want him to be a super student."
Wolff said that pushing kids to succeed can have the opposite effect.
"If you find yourself as a mom or dad pushing your kid to do things -- like try out for a travel team or to go to practice seven days a week -- and the kid doesn't have the enthusiasm to do it, ultimately the kid is going to walk away from the sport. And probably a lot sooner than you anticipate," he said. "And when kids walk away they don't come back."
Burnett said parents need to stay calm if their child makes a mistake in a game.
"I think the biggest thing that sports teaches kids is that it's OK to make a mistake," he said. "In baseball [if] you hit .300, seven times [in 10 at-bats] you were out. When you make a mistake it's OK. You can learn from it and move on."
He said that if parents overreact, kids are more likely to get emotional and beat themselves up over a mistake instead of making adjustments to fix the problem.
Burnett also said that parents should make a real effort to praise their children for the good things they do in a game instead of focusing on what they need to improve. He recommended a ratio of four positive comments for every negative comment.
"When you praise your kids, make sure it's specific -- 'Good game, nice try,' doesn't make it," he said. "But (if you say) 'Hey, I like the way you got the ball back to the cutoff man,' then the kid hears that and visualizes that and says 'Hey, I did do good there.' "