Lydia's mother. She takes a job as a substitute teacher after Mr. Harris and Ms. Blake "disappear."
She claims that she will be teaching Biology, even though the students had all been previously taking Physics. This appears to be a writing gaffe.
Peter talks to Ms. Martin in the hallway at school, claiming to be from the Health Department there to set up hearing tests. He's really there to get Lydia's attention and get her to visit him.