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It seems to me the focus should be on the kids rather than the social sensitivities of the adults involved in teaching the course. In my opinion, the teacher described is being persistently inappropriate and the fact she seems to privilege relating her own experiences over answering the children's queries indicates she is indeed using the class primarily as a sounding board.
Saying that, as another letter writer noted, this behaviour indicates she may herself be unstable and unable to discern the appropriate boundaries. Therefore I agree with those who suggested she should not be initially approached. I personally would try to come to a consensus (if possible) with the other teachers then take it to the next level of authority.
Cary is right in saying that if the parents hear of this teacher's problematic methods there is a risk of the class being shut down or otherwise curtailed--which would be the worst thing for the kids involved. The second worst thing would be to allow this woman's monologues to further unsettle teenagers who may already have their own insecurities around sex--insecurities which are not being addressed in her class.