I don't mind crossdressing, especially because I have naturally short, black hair; it's definitely a possibility. (picture uploaded is similar to current hairstyle; the problem is that it is asymmetrical)
I'm currently in high school as well, about 5'4, 100% East Asian, with a nonchalant personality. Oh, and body? *cough* 90 lbs *cough*
In terms of difficulty, it doesn't concern me too much, but I do not want to cosplay a character with a school uniform / sailor fuku.
Suggestions and recommendations are greatly welcomed!
Thanks in advance.

[ Edited Apr 4, 2012 ]

First person to come in mind: Nana Osaki from Nana. She's an amazing character, the manga and anime is wonderful, and she wouldn't be caught ever wearing a school uniform.

Thats just a suggestion ^-^