Arielle Tepper fondly remembers her first Broadway show, Annie. "I couldn't believe how excited I was," she says. "I'm looking around the theater and thinking, 'Everybody's sitting in this big room having a really good time, and that little girl onstage is making that possible.'" The problem is that kids who get excited about shows like Annie soon reach the awkward age: too old for Simba and too young for earnest dramas about bad marriages, or revivals of Broadway musicals that your parents used to go to. Still do.
For years, theater has had trouble attracting the kind of hip young...