My Teacher is an Alien is a science fiction novel for young readers, written by Bruce Coville and first published in 1989. The story revolves around Susan Simmons, a sixth-grader who becomes suspicious of her new substitute teacher, Mr. Smith, when she notices his strange behavior and discovers a mysterious device in his office. With the help of her friend Peter, she embarks on a mission to uncover the truth about Mr. Smith, and discovers that he is not from Earth, but from another planet. The two students then find themselves involved in a mission to help Mr. Smith repair his spacecraft and return home, while also trying to avoid the attention of the sinister school principal who seems to be working against them. The novel is a fun and exciting adventure that combines science fiction elements with themes of friendship, trust, and acceptance, making it an engaging read for children who enjoy stories about space and aliens.