In my school i feel like the underdog, what should I do to not feel this way?

First evaluate what is making you feel like you do. If its something you can change, such as the way people perceive you, try and change it. If its something else like others looking down on you for race, , religion, or income just try and remember that none of these things are thing your in control of. Most people will pick at you only if your an easy target. I'm not suggesting that you are aggressive or get into fights. But if you act confident (fake it till you make it) people will be less likely to har you.