How to be more preppy?

Ok so I'm 13 almost 14 & i'm sorta scene/indie/alternative. I listen to music like Chase Coy, Jamestown Story, Cady Groves, Stephen Jerzak, Great Big Planes, Vampire Weekend, MGMT, Two Door Cinema Club, The Fratellis, The Smiths, and Fugazi. I wear lotsa skinny jeans, colorful on ups, floaty tops, flip flops, TOMS, cuffed capris, wooden beads, friendship bracelets, & the only things i do with my makeup are eyeliner & curling my lashes. My parents decided they wanna send me to a prep school next yr. Idk why. But all the sudden I started wanting to look in name brand stores & stuff. I also rlly like playin lacrosse. And idk why but I started having things for clean cut boys with polo shirts & slacks. So how can i go more preppy without 100% losing mah indie style, or at least so tht I can look kinda indie over the summer when i'm home. Thnx!