I understand and have had some not so good experiences with some people who have control issues. They can be dangerous. But anyone using common sense (which may be absent in this case) would recognize that in these circumstances, after the deed, the student probably has more leverage for control than the adult. A teacher should recognize this before that fact. What is wrong with these people? Rhetorical question.
You have a point. I was a sexually abused teen and I was sad to lose my best security the day I turned 18. Being jailbait was like concealed carrying.
Should be the first and last thing the adult thinks about. Do i really want to give this person so much power over me?