Willimena is starting third grade when she finds out she'll be in Mrs. Sweetly's class. Mrs. Sweetly is the meanest teacher at the Harriet Tubman School. Willimena decides that to avoid trouble, she will be the best, nicest student Mrs. Sweetly has ever known. The plan is working until Willimena loses the class guinea pig. How will Willimena cope with Mrs. Sweetly now that she's no longer the perfect student?