All three are correct in a grammatical sense. It's a question of what you are trying to say. "Passionate" is not very likely to be used in terms of how a teacher interacts with students. It is typical for people to say that someone is passionate about his or her profession. However, it's a word that has a lot of meanings, some of which you have to be careful of.
"Warm" and "enthusiastic" have rather different meanings. I'd say they are both acceptable.