Dating former high school student
Sometimes they publish papers with their former students as coauthors, based on work they previously did together.
In particular, the idea that it is disturbing for a much older (adult) to date a much younger (adult) may be more of a societal taboo/hangup than anything that can be rationally justified.
It is also true that most romantic relationships come with a certain amount of push back, and some kinds of romantic relationships still get a lot of push back for things that many/most of us feel strongly are absolutely unproblematic: e.g.
inter-racial relationships, same sex relationships. (In fact, I am very sorry to say that if your relationship is not inter-racial or same sex, any push back you get will probably be mild compared to that, and if it is, that will increase the push back considerably.) I recommend weighing the possible costs of such a relationship against the possible benefits. I know people who started dating their student, or even getting into marriage with them, and that's fine here.
Once I am done with the short-term scenario where I have influence over a person, such an expectation would impose notable cost/harm without really providing significant benefit. Just because it seems unfair to you not to do it doesn't mean its ethical to do it.
There are many situations in life where one has to step back and put ethics above the personal [email protected] : There's a difference between morality (right/wrong) and ethics (which has more to do with the expectations of society/culture).