[Kate*]

I can see why you wouldn't want to announce it in front of the class when they ask for nicknames and preffered names. I would suggest talking to them after class, if they ask about it give them as much or as little detail as you want, they pretty much treat you like an adult so they shouldn't ask too many intrusive questions. I would pick the name that you like the best, since you will have to live with it, but remember that the college won't officially change it until you have it legally changed.