As I argued before, this strikes me as quite wrong. It might be unprofessional conduct that would justify firing the employee, but not sending the teacher to prison.
The “abuse of a position of power” rationale doesn’t work here, I think; a teacher has no more power over the student than the typical employer, or police officer, or many other people. Yet we deal with the extraction of sexual favors through threats in those contexts by requiring proof of abuse (whether in a civil case or a criminal extortion case), not by just presuming it. And the law applies to even less powerful employees as well.
Nor does the psychotherapist analogy work; the teacher-student relationship strikes me as quite different from the psychotherapist-patient relationship: It involves far less likelihood of emotional fragility on the alleged “victim”‘s part, and a professional relationship that is far less likely to involve revelation of deep secrets and the seeking of important life advice. Criminal punishment, and especially felony punishment, of sexual behavior should be reserved for genuine force, fraud, imposition on children, or situations where there seems to be a real risk of extraordinary psychological or physical harm, or harm to social institutions — not to consensual sex between adults, even when one adult is a school employee and the other is a student.
Thanks to Fred Ray for the pointer.
UPDATE: I originally said that psychotherapist-patient sex doesn’t, to my knowledge, lead to felony criminal punishment (as opposed to professional patients). But Kent Scheidegger pointed out that at least in California, it might: California law treats such sex as a misdemeanor, or a felony if it’s committed with two or more “victims.” I’ve therefore revised the post to focus on the difference between the teacher-student relationship and the psychotherapist-patient relationship. (I should say that the California law also criminalizes sex between physicians and patients, including when the patient is no longer a patient but “the [professional] relationship was terminated primarily for the purpose of” having a sexual relationship. I would likewise oppose criminal punishment in that context as well, and quite likely even professional discipline, at least unless something beyond a physician-patient relationship is present.)