I've been waiting for this for a long time. Just before the start of the present semester, I received the following email (slightly altered for confidentiality)
Dear Prof. Heppner:
I am enrolled in your Bio 101 class as Brittany Caswell. On September 8, I will become Jason Caswell. I will bring all the papers, but I'm asking that you refer to me in class as Jason, right at the beginnng.
How could I refuse? My reply was:
Dear Mr. Caswell:
As you will be one of 319 students in a giant lecture hall, it is unlikely that I will be referring to you by any name during lecture. The issue will be a bit more problematic in laboratory class. I am sending you the name and email of your teaching assistant. You should contact her immediately to avoid any confusio.
Best regards,
F Heppner