Assuming you are in good physical shape... Tops: Nice snug t-shirts or halter tops. They shouldn't go any higher than an inch above the belly button. Me personally, I like the ones that stop right under the belly button. Yum yum.
Pants: Skinny colored jeans look great. Even blue colored looks better than normal denim. Short shorts (not with tights) leggings, and skirts that stop maybe 2" above the knee look good to.
*I'd advise you not to wear halter tops with anything but jeans. Gives off a kind of whorish vibe.
Shoes: Colored converse (preferable high tops), Vans, and Keds all look good.
Also, dark colors are bad. For everything. Wear bright, happy colors. Makes you more noticeable.
Well I'm in high school too maybe we can like have conversations about this sometime cus sometimes I am really clueless and it does depend on your body type but I'll help you if you help me with something else
Something that covers your body. For Christ's sake I'm so sick of highschool aged girls running around in shorts that don't cover their asses and deep v-necks that expose the tops of their push-up bras. /rant
Anyway, just stay classy and play with different colors and patterns, jeans and a cute top are never out of style and I do like the scarf thing that's been happening for a while. I love the look of ballet flats as a shoe choice as well.
I wear uniform to school, every day. But I usually wear hoodies and stuff. My classmate (a guy) has ever worn sweater on top of it with matching colours and it's not bad. LOL
Wear comfortable, preppy clothes. I suggest that you buy a lot of tops and have at least three pairs of footwear fit for school. It also depends a lot on the colors and patterns that you can pull off. Your height and body type matters too. So be a bit more specific?