To see your teacher (past or present) in a dream suggests that you are seeking some advice, guidance, or knowledge. You are heading into a new path in life and ready to learn by example or from a past experience. Consider your own personal experiences with that particular teacher.
Alternatively, it may relate to issues with authority and seeking approval. You may going through a situation in your waking life where you feel that you are being treated like a student or in which you feel you are being put to a test.
If you dreamed of a dangerous or evil teacher, or just an incompetent one, you may be getting bad advice from someone close to you.
If you were the teacher, see “Teaching”, below.