In college, I requested all my teachers to call me by preferred name. I prepared printed letters but also spoke with them personally. It generally wasn’t a problem. Just appear confident. Here’s a sample letter you can send your teacher:
[Instructor Name. If unknown, use “To whom it may concern”],
My preferred name is [Your Name], and I use [/] pronouns. All my emails, assignments and exam papers will be under this name, but the grades you submit should be under the name in the school system.
For your reference, my Student ID number is [ID #].
Should you explain that you’re transgender? It’s completely up to you. I did.