I would say it depends on the laws of that state. If the law allows 16 yo girls to have consentual sex with anyone, then why should a teacher be banned?
Umm, because the teacher is in a position of power over students, because it would be unfair to other students, and because it is morally reprehensible.
For the same reason that military officers aren't supposed to have sex with those under their command.
This isn't immediately apparent to you?
Because the sex compromises the teacher-student relationship, and therefore the ability of the teacher to educate that student and all the other students in the classroom. No freedom is absolute; reasonable exceptions in specific situations may be necessary to be written into law, and this is one of them.
"I would say it depends on the laws of that state. If the law allows 16 yo girls to have consentual sex with anyone, then why should a teacher be banned?
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I agree. I think it should be an offense for which they should get fired but if the people involved are over the age of consent in the state I don't think criminal charges should be filed.