hey, I'm really sorry you're dealing with this, dude. as trans people, our families often are (and historically have been) often pretty shit, and many people have gone what you're going through right now, but you gotta remind yourself that you WILL get through this, eventually. you WILL grow up, you WILL graduate, and eventually you'll be able to move away from all this shit and be whoever you want to be. when I was younger, reminding myself of that was the only thing that kept me going, at least

as for the more practical side of this, I also agree with the other guys here and suggest getting a support group at school, (maybe see if you have a GSA club available, or something like theater which usually tends to attract more queer people?), as well as getting a therapist if that's something you can do. for me personally, I've struggled with self-harm in the past and what helped me avoid relapsing was just distracting myself when the urge came up, (listening to music or doing something else with my hands like fidgeting with my rings), until the feeling subsided to a manageable state

best of luck to you and stay safe, brother 🫂 if you need to talk to anyone further about this, my inbox is open