I would really recommend not worrying if you need to be wearing "sporty prep" or "nerd" or even "conservative christian". Just wear what you are comfortable in, what makes you feel pretty. If a guy is going to fall in love with you then he will for the traits you mentioned - not the designer on your labels (and if he does then he's shallow and not worth your time).

Your 11 - enjoy your life. personally your too young to be thinking about "style" and fitting in a certain Niche'. *proof yet again i feel old* Go enjoy your friends, enjoy your life, and live it as best as you can before it starts getting a lot harder and you get a lot more worries besides "what movie am I going to see tonight".