Welcome to the booth! I agree the Student TD is the appropriate term. It tells us that you are the most senior technician at your school. Although what that means varies a ton from school to school. Some folks do find it a little insulting to the lifetime it took them to reach their position for you to
call yourself a T.D. The truth is what you do as the head theater technician in a high school has very little to do with the job of a professional T.D. I doubt you spend the majority of your time analyzing designs, figuring how you can implement them without breaking your theater's budget, and then overseeing the hiring and firing of shop staff. In a large union professional theater the T.D. never touches a tool, spotlight, or
microphone... they are a manager. In smaller theaters and community theaters the T.D. does all the budget stuff and is often also the head carpenter... and a
bit of a teacher as well.
Anyway welcome to the booth. Have a good time use the search function there's lots of information there and ask questions when you need help.