This undemanding but warmly satisfying story has all the light throwaway humor of 51 Sycamore Lane (p. 642. J-244), but it's miles ahead in probability, sensitivity, and general durability. The slight plot concerns Thad Smith's campaign, per the title, to GSOMMM (the extra M is for mousy, because Maggie squeaks) to prevent her announcing to every kid in school that she's caught him in the sissy act of cooking. To further his project Thad even volunteers to be the flog in the class play opposite Maggie's princess, but when he finally gets the goods on her -- after a dramatic performance when Thad, ""so nervous he could croak,"" comes unzipped from his frog suit and Maggie's improvisation saves the day -- he finds he can't go through with the expose. From the opening scene in the school cafeteria, complete with lunch bag auction and flying celery, children will feel right at home. Ben Shecter's gently amusing drawings echo the story's mood.