SCHOOL'S OUT

After three books recounting his checkered third-grade career, likable Lucas Cott has a busy summer. At first, he's not pleased to learn that a French ``oh pear'' will be coming to learn English and baby-sit, even though his parents assure him that Genevieve's chief responsibility will be watching his twin brothers, age two. Lucas soon proves that he, too, needs watching; among other pranks, he climbs a painter's ladder and learns how much easier it is to go up than down. More strictly supervised as a result, he wheedles Genevieve into buying extra sweets when they go shopping, but she's a smart, sensible sort who soon ``has his number.'' By summer's end they're good friends, while Lucas has resolved to set his brothers a good example instead of being part of the problem. Hurwitz's perceptive observation of commonplace incidents transforms them into entertaining, richly insightful vignettes. Lucas continues to be an engagingly realistic blend of mischief and good intentions; other characters, especially the resourceful, good-natured Genevieve, are also deftly drawn. Totally satisfying. (Fiction. 7-11)