What are the connections between teachers in Harry Potter and teachers in Little Brother?

In Little Brother, Marcus's original teacher teaches a controversial class in which she sparks a debate by going through the controversial history of youth movements in California, such as the Yippies and the FSM. Marcus really like this teacher. she was replaced by another teacher, a teacher who was far more right wing and who fought with Marcus at every turn. She sent Marcus to the Principal's office for an opinion he had in class where he was suspended. Like in Little Brother, Harry Potter also has a teacher who fights him at ever turn in Dolores Umbridge. Professor Umbridge decides that students at Hogwarts do not need to know how to defend themselves against the Dark arts, prompting Harry to organize secret meetings of students to teach them how. It turns out that she is part of the dark side of the magic world. In both these books, teachers can be a guiding light, helping the student find their beliefs and put them into action, or they can be a roadblock, forcing the student to either back off from their beliefs or forcing them to fight them or circumnavigate them to find themselves.