Your only should.
Clothes is an integral part of our life. And we are learning to use it well since kindergarten. Felling of style firstly come from our surroundings, and mostly from people around us. In a young age we are simply copying what we saw and wearing only what we were told to wear. But in high school it's kinda competition. You should try your best to feel yourself confident. And a great deal of being the best is your appearance. Teenagers are dependent on their style, otherwise they will suffer.
Year to year you are becoming more experienced in clothes matter. But when you are going to be free from "should" chain, you can lose your style. Lose it only because of diversity of choices. You can be whoever you want. And you must manage such power, in order to be successful.
For example, if you are visiting your possible employer then maybe you should wear something more suitable to such occasion, than jeans and tank top, or maybe you shouldn't, it depends. And if in past years you were listening what other are saying then now you mostly use your own opinion. And in such case you can notice, that you aren't waiting for people to react to your new coat, but you are starting to react on it by yourself, by feeling confident.