Three justifiably friendless fourth graders are sent to see the principal, who can't talk to them just then and sends them back to class; in a moment of ill-considered panic, they run out the door together and hide in a dumpster during a fire drill. Since they know the janitor saw them leaving, they pass an anxious weekend plotting and worrying about what will happen on Monday. The punishments are minimal--the janitor hasn't reported them--but the experience enables them to change their behavior: best, they become friends. Park's use of funny-sounding, probably unfamiliar words will elicit belly laughs, as will her characters' outrageous predicaments. The nervous new kid who says and does the wrong thing, the officious tattler, and the puny genius who invites teasing--all are familiar types: but as drawn here, they'll win empathy as well as laughter. A minor demerit: crawling into dumpsters is dangerous. Sure to be a hit.