More kids and adolescents are getting sidelined by the price tag for youth sports, studies suggest, and critics worry that one day, organized leagues will only be an option for upper-class families.

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Darryl Hill, CEO of Kids Play USA, cited a huge shift towards "commercialization" among youth sports, noting free participation is hard to come by these days.

"This shift has been dramatic over the past few years and is getting bigger and bigger," Hill said, pointing to the emerging popularity of travel teams for sports such as soccer, dance and baseball. "Not only are there the expenses of being on the team and being a member of the team; now there are expenses related to travel, which can be quite extensive."

More schools, meanwhile, are charging fees for children to participate in their official sports programs. In a study by the University of Michigan C.S. Mott Children's Hospital, more than 60 percent of respondents reported a pay-to-play scenario for middle and high school sports.

Hill said the result has been an "abysmal" decline in youth sports participation over the last quarter of a century.

"It's biting into the middle class budgets -- no question about that," he said. "And certainly, it's almost impossible for low-income or kids from underserved families. They just can't foot these bills."

Because of this, Hill said, many kids are missing out on several benefits that go beyond health.

"Kids learn how to get along with each other. Kids learn how to play by the rules," he explained. "Kids learn time management. Kids learn how to compete, but they also learn how to lose."