Third Grade is Trouble by Barbara Baker

Some Third graders have sweet, friendly Mrs. Lane for homeroom. Liza's stuck with Mrs. Rumford - the meanest, strictest teacher in school. In her class, there are no nicknames allowed, neatness counts, and everyone has to have two sharp pencils at all times. Liza can't seem to do anything right and she wonders how she'll survive the year. Then she meets the new girl, Bridget. Can the two of them tough it out together?