How to respond with being misgendered at a new school? (ftm)

I have started sixth form in a new school, and i think only the teachers know that im trans. I pass pretty well, as people always call me sir or treat me like a boy, but i am kinda clockable for my height as im legit 5'1 and i look like im 12. The teachers treat me like a boy, so thats fine right, but the students, like the boys are addressing me using girl pronous. I just dont know how to respond to them using those pronouns and i don't know how to correct them.