The lack of moral vision by so many here is worrisome. The teacher was in the wrong. Both ethically and morally. As I have stated in other posts I am not that concerned with the age difference. Had a relationship between two single people where one was not constrained by ethics about who they could be with I would look askance at somebody demanding a 17 year old be protected from being with a 27 year old.
What concerns me is that she was his teacher. That and how many are willing to give women who take advantage of adolescent boys high fives provided she is attractive.
Who gave the woman high fives for what she did? I didn't see that at all in one hundred and something plus posts.