How can I hide the effects?

So I'm 18 and I live with my parents and I want to start HRT, but nobody irl knows that I'm trans, and I'm scared of telling it to anyone.

I think I would be able to hide it from my family somehow, but the biggest problem is that I'm still at high school and I would be for another 2 years. The biggest problem is PE, because I don't know how would I be able to hide the breasts grow in there, I think I would be able to hide it somehow from all the other situations (idk how but I'll think of smth), but I can't for my life find any solutions to PE in school.

Any ideas?

Mby isn't there some method to make the breast grow slower? Mby instead of injections using pills sublingually without AA?

Edit: I'm talking abt DIY hrt btw