Hey i am starting high school and i have been playing the gitarre 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 Mitmachen you.

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