It seems the concensus is to report it now, save the note and get this out in the open with your superiors. Bottom line here is; "cover your own ass because this could go bad". I agree with that: cover your ass. But it also seems as though the real danger here is not legal liability but your reputation and standing with your employers, co-workers and students. I believe the statement made about you being allowed to have sex with anyone of age is true. However, that does not preclude the school from having its own set of behavioral standards, and, sexual harassment lawsuits being the gold mine that they are, ANY appearance of innapropriate behavior will be met with potentially career-ruining actions by your employers. They want to cover THEIR asses too.
That being said, I agree with Mantis on this one. She's just a kid still really and you don't know for sure that shes a psycho out to hurt you in anyway. In fact, you don't even know it was her. What if someone in the class who has something against her put the note there...Not looking to get into conspiracy theories, but its important to consider alternative possibilities of how this came about. It could be many different ways. Its also important to consider alternative possibilities of how it could turn out.
Not saying this is going to happen, but it could and, to me, its a worst case scenario: Lets say she does go scitzo on you. Well, in that case there's not much you can do anyway. What I mean is that the situation will blow up and wether or not you kept and reported the note will be irrelevant. There will be many more uncomfortable exchanges (more notes, her following you around, her telling other people lies about you that spread around). This will surely provide you more physical evidence and, through litigation, you can eventually save your career, but in the meantime, accusations will be flying all over the place. Her friends will say "she said she was seeing him on the side, I swear its true" or other such things. Even if you had reported the note from the outset, she will claim that you wrote it yourself or that it was a note you had willfully accepted from her and you only talked to your superiors to discredit her because she wanted to break up or some such nonsense (there's a million possible lies and evidence will, at first, not be a factor in how other people judge the situation). Other people, even your colleagues, will hear so many rumors they won't know what to believe. How would your superior, even the exact person you reported it to, know for sure that something hadn't been going on between you two before you turned in the note? It could be turned against you. It will be a shit-show and will ruin your reputation and probably get you fired even though you did nothing wrong and folowed protocol. From here on in just read some of the later chapters of The Crucible to get a general picture.
Thats the worst case scenario and, to me, it is highly unlikely that that will happen. However: the issue over wether or not you do indeed report the note is moot if she is spiteful, malicious or crazy. That cannot be denied.
Reporting her to authorities/school officials may make spiteful behavior from her more likely. Avoid any course of action which increases the likelihood of the worst case scenario.
I say: be cool. I did PLENTY of innapropriate, dangerous, idiotic, and offensive things when i was a student in college (nothing really analagous). But I was never malicious about them and almost always; I regretted them. I think the real way to cover your own ass is not by handing in the note but by remaining calm and being prepared. Don't act in any way that could be percieved as innapropriate, never let yourself get caught alone with her, and (if applicable) confide in a good friend at work who can help you get out of a potentially bad situation if you get cornered (e.g. he comes to your class when its due to end so that there is no way you can get caught alone with her). Forget about the note, pretend you never even saw it. Dismiss it in your own mind and make it so that if she wants to ask you about it; she does so in the presence of other people. If you get more such letters/notes, then you are indeed being harrassed and should tell your superiors. I just don't see how reporting it is a magic cure and, in fact, feel it is more likely to end up hurting you.
If she comes up to you at the end of class (with others around) and asks you about it, don't make a scene but say (sternly) something like: "Please don't ever do that again its uncomfortable for me and could get me fired. If you do, I will have to inform the dean." If she cannot accept that, and comes back with more innapropriate notes or propositions then, on the bright side: you will still have physical evidence, but on the darker side: its pretty much out of your hands anyway....
