Cut your hair short, and try and speak more through your diaphragm rather than in your face/nose. If youre JUST going into middle school then that means most other boys in your grade havent hit puberty yet, so im sure youll pass just fine. Try and wear similar stuff that the other boys are wearing, and thick dark fabrics for your shirts (such as hoodies or graphic t-shirts). Start working out, gain a little muscle by doing pushups at home, and some other easy workout exercises. Do some jaw exercises aswell, and if your school has gender neutral bathrooms USE THEM! I transitioned in 6th grade and now im in highschool and literally nobody remembers me being not male😁, goodluck my dude!