I misunderstood the question.......how come I can't delete the answer.... ( TДT)

There is not a quit difference between 教師 and 先生. I'm working as an English and I use both. 教師 sounds a little official and focuses on being a teacher as a job, and 先生 sounds more general and focuses on his/her personality. But the difference is so tiny bit that you don't have to worry about it. がんばって！！