Betsy Byars' daughter debuts with a promising tale about self-esteem: Marty Malone, new boy in third grade, is good at math but so bad in gym that he's always picked last. He spends most of the book plotting to escape the dreaded class--until a teacher and a fellow classmate let him know that he's not alone. Reassuring but too obviously didactic, this is distinguished by Duffey's skill in making Marty's inner feelings ring true--a good omen for future less-purposive books. Illustrations not seen.