The purpose of school uniforms, which I assume this is, is to make it so basically nobody looks good in them. From the way you've described it, I seriously doubt you'll find a way to make this uniform work for you. Sorry. :(
Make your hair badass, put some gel in it and play with it. Your attitude and personality can make it hot or unnoticeable.
What Guys Said 1
did you consider taking trousers you're talking about to a tailer, if they were lousy then it's easy to make them tighter, tailors know their job, they'll just take your measurements. and one thing I used to do, is taking any uniform piece of cloth with me when I go shopping, and try to find an exactly identical piece that they won't tell at school it's the standard or not, just find trousers that fit you the best and still look exactly like your school's.