How Kids’ Sports Became a $15 Billion Industry.

Joey Erace knocks pitch after pitch into the netting of his $15,000 backyard batting cage, the pings from his metal bat filling the air in the south New Jersey cul-de-sac. His private hitting coach, who’s charging $100 for this hour-long session, tells Joey to shorten his stride. He’s accustomed to such focused instruction: the evening batting practice followed a one-on-one fielding lesson in Philadelphia earlier in the day, which cost another $100.