salut i am starting high school and i have been playing the guitare for a while and i know a few people that can play drums and bass, so how do i start a band?

Ask them to rejoindre you.

First see if toi have permission from your parents. Then find a place toi can practice together. It can be anywhere, like Parks, garage of any member, ou a coffee shop. After toi have done these things decide a cool name for your band depending upon what kind of band toi are making, and ensure that it isn't same as any other band. toi can make a Rock and Roll, Emo, Punk, ou any other genre toi like. Then after toi have decided the name start practicing. First as beginners toi can sing covers of your fav songs and later toi can write songs on your own. To popularise your band toi make band posters and paste it on public places so that people would come to know about it. toi can organise small shows at occasions like your friend's birthday ou some get-together parties.
So, get going and rock it!! I think this will help you. :)