The Worst Witch All at Sea

Publisher's description: "On Mildred's first day back at Miss Cackle's Academy for Witches her beloved cat, Tabby, is banished to the kitchen, and when the class goes for a week by the seaside Mildred stows Tabby away in order to take him along. But trying to keep him hidden from Miss Hardbroom and the ghastly Ethel Hallow leads Mildred from one disaster to another."