Principle Dave is the principle of the high school that Duncan attends.
Principle Dave first appears when Duncan and Troy are sent to his office for their altercation. He gives them a choice of either suspension or have to work together to clean up the marks left by Duncan's fire-breathing.
He seems to be fair and just, but also very stern. He also seems to have a dry sense of humor since he remarks that Troy has been in his office so much that his name should be on the chair in bronze.