You are good enough. Every challenge you face is a test of perseverance. Don't let other people drag you down and whatever they may say to offend you should be ignored. When it comes to bullies the silent treatment might be the best option if it's verbal abuse. As for your teacher making you do the higher tier science paper, don't you think you should tell the head of the science department about this? You shouldn't be mistreated by teachers or your peers, but keep on going you're stronger than you know.