Stand Tall, Molly Lou Melon by Patty Lovell (2001)
Molly Lou Melon may be tiny, clumsy, buck-toothed, and with a voice "like a bullfrog being squeezed by a boa constrictor," but she doesn't mind. Her grandmother has utmost confidence in her, and tells her at every turn to believe in herself. "Sing out clear and strong and the world will cry tears of joy," Grandma says. But Molly Lou's self-assurance is put to the test when she moves to a new town, away from her friends and beloved grandmother. During her first week of school, Ronald Durkin taunts Molly Lou Melon in the dull-witted but sharp-edged manner of career bullies, calling her "shrimpo" and "bucky-toothed beaver." Our heroine barely flinches as she systematically sets out to prove herself, and Ronald Durkin ends up feeling pretty foolish.