How do you think girls should dress? Are brand names and fancy clothing really necessary?

I don't wear brand names AT ALL. Yet people my age think you must wear them to fit in. I personally think that a sweatshirt and jeans and nice shoes are enough. I wear it and some people think that the sporty look is really pretty on me and on other girls. Wearing a dress to school is going a bit overboard. It's SCHOOL not a runway. I'm not against nice clothes or anything (I like to dress up once a month), I just think that you don't really NEED to dress up that much at school. What is your opinion on what teen girls wear to school? Do you like it? If you would make your own dresscode, what would it be?