IN the late afternoon chilly dark, the pop star Justin Bieber, 15, emerged from the radio station in Providence, R.I., where he had just been interviewed. As if on cue, a large pack of tween girls screamed and pounced.

So did their mothers.

“Justin, my daughter Elizabeth is going to your show tonight!” shouted one woman, shoving girls out of the way to push her cellphone camera in Mr. Bieber’s face. “Want a play date with her, Justin?”

A shriek, presumably from the mortified Elizabeth: “Mom!”

Justin, blessed with excellent mop-top hair, gamely pushed through his jet lag to produce a camera-ready smile. Then his mother, Pattie Mallette, rescued him: she and his entourage hustled him into a van and sped away.

“The mothers are the worst,” Ms. Mallette said later, sitting in a hotel lobby armchair, reflecting on parenting one of the few teenagers in America who, for his own safety, can hang out at a mall only when others are in school.