How do you handle a Bible class teacher who is teaching false doctrine?
I've just read your answer to a person who was asking for advice because his Sunday school teacher told him that Cain was the result of Satan having sexual relations with Eve. You suggested that he find a different Sunday school teacher. However, in many churches you don't choose your teacher; rather, depending on your age or perhaps some social category you are assigned to a specific class. In any case, I think the pastor or leaders of the church should know that this person is teaching things that aren't biblical because even if the person were able to choose which class to go to, those who remained under the teacher in question would still be receiving false teaching.
If the material being presented was not approved by the leadership of the congregation, then letting them know should result in a different teacher for the class. If the material was being presented with the leadership's approval, then the person needs to find a different church -- one that teaches the truth -- which will result in having a different teacher. One is not trapped having to stay with a group that is teaching false doctrine. In either direction, a different teacher is found.