How can we start a band as high school freshmen?

I am going into High School this year, and my friend and I love (and I mean L-O-V-E) music. I was thinking we could start a band. I sing and play guitar and a little piano. She sings and plays drums and a little piano. Could we start a band with only us like The Wreckers, The Veronicas, or t.a.t.u ? Would we need more? If so, what do you suggest we do to get more people? Detailed answers (i.e. no 'just put up posters, lol :P')