A distinguished writer is at the top of her form in a sharp and sassy tale of two fifth-grade troublemakers. Thrown together by the alphabetical seating arrangement, Margalo Epps and Michelle "Mikey" Eppinger cautiously form an alliance that deepens into a stormy but firm friendship. Both are bright, tough, acerbic, and fond of stirring things up, but their differences really spark the relationship: Mike), is public and aggressive, willing to punch the class bully in the nose or dye her hair green, while Margalo prefers to start damaging rumors or slip a dead squirrel into a prissy offender's lunch. Voigt (The Wings of a Falcon, 1993, etc.) creates a set of complex, believable, still-developing characters, and parks them mostly in a brilliant, very experienced teacher's classroom to explore what makes them tick. The girls are motivated not by malice but general anger (Mikey) and loneliness (Margalo); most of their imaginative, carefully directed pranks are paybacks, less hurtful than horrifying and frequently hilarious. Unrepentant to the end, this pair of unlikable but admirably capable mavericks outmatch even Barbara Robinson's Herdman family for sheer sand. (Fiction. 9-12)