5 years ago: Year 7 me had recently done an oral presentation on writing a letter to grade 6 me, which seems somewhat fitting.
Don't drop the effort. I know you had much higher expectations for highschool, it isn't going to be until VCE that you start learning new things at school but keep going.There's no reason at all to stop learning, even if teachers aren't providing you with the "advanced work" they said they would. Go online, start teaching yourself another language (doing Japanese at school doesn't count) before year 9 so you can learn more before VCE hits, actually prepare your speeches instead of skating by on the fact that you'll get good marks without trying, because that won't help you grow. Do some of the uni courses available online. There is heaps to learn and you are more than capable of learning it.
People will stop associating you with your family, it just takes time. Your efforts in bettering yourself do pay off, and there are tools to help you with productivity and mindset. No one is perfect, and no one has to be. You are not a disappointment to anyone, including your past or future selves. Don't hang your hopes on other people changing, you can't control that, only yourself, and even that takes time in addition to the effort. Sometimes it also takes time to put in the effort, and that's ok. The conflict isn't your fault, and you are never forced to leave. I still haven't figured out forgiveness yet, but you aren't as bad at it as you think, and not associating with people can be good.
Also, mum was wrong about vegetarianism being unhealthy.