The appearance of a teacher in your dream is a positive sign. Often it indicates that some balance will be found in the personal life. This balance will likely be quite lasting as if a long terms solution will be found for some emotional issues that you might have. There are however a several interpretations.
One interpretation of seeing a teacher in your dream is that you might have a rather burning question for which you would need to talk with someone in order for the question to be resolved. It might also the case that you need to take and advice from someone.
If in your dream you see a teacher that teaches about any artistic discipline it indicates that you need to take the happenings in your personal life in a more serious manner. You might try hard to avoid any long term responsibilities but your friends might not enjoy this. If you are in a romantic relationship the time for being more committed might have come.
The meaning of a dream in which you see a teacher teaching about rational and scientific matters is that you will be quite successful professionally if you choose to start new things and new projects within the next few months. Simply put, the next few months are a suitable period for exploring new areas of your professional development.
If you dream that you are a teacher yourself in the dream it means that you have a rather strong thirst for knowledge and skills. You might even enroll yourself into some form of schooling within the next few months. On a more general note a dream like this indicates that you still posses a youthfulness of your mind regardless of what your age might be.
Seeing an old teacher of yours in your dream indicates that you will soon reestablish an old friendship of yours.