For the younger set, tough moral choices treated with respect and memorable humor. Rosie is ``Camper of the Week'' because she really is good and dutiful; she's also so nice that her friends don't hold it against her. Still, the true heroes of the moment are fellow- Badgers Rhonda and the twins: harmlessly but effectively, they get back at bully Bernice by putting minnows in her bed. Rosie (who is ruminating about the effects of her own behavior) is actually an accomplice; she creates a diversion at the crucial moment. The others are punished (they have to stay in the cabin during a special treat); in a deft blend of real conscience with the practical realization that being ``good'' may not always be best, Rosie quietly decides to join them. Adroitly catching every nuance, Schwartz depicts Rosie sorting through her dilemma in crisp dialogue and telling action. Her good-humored illustrations focus on the essentials: just enough background to give a whiff of the camp milieu; the campers drawn with a few spare but revealing lines. A real winner. (Picture book. 5-9)