Hi Robyn and welcome to TGH.
Personally, I would leverage any support from my legal guardians who still play a role in your academic primary education. Together you speak with administration about your intentions offering them the opportunity to also support you. There are legal requirements for administration and staff that you should familiarize yourself with as well to know what is required of them.
I wouldn’t try to fool you into thinking this will be rosey. There will almost certainly be resistance and pushback from classmates who just don’t get it. Steel yourself for that day. You may be breaking ground in their lives toward understanding and acceptance.
Being an adult site we don’t have much experience with support of people in primary education areas. You may likely find much more extensive information on a youth oriented site for which we have provided links at https://transgenderheaven.com/transgender-youth/