Welcome to the forums. I really hope that you are able to find the support you are looking for here.
I am so sorry you are feeling so disconnected, upset and stuck. High school can be exhausting and very cliquey and other students can be pretty awful to each other. Plus changing schools can be difficult at the best of times, I can only imagine that the lockdown/restrictions would have made it even more challenging. It is great that you have felt able (and had the courage!) to reach out to teachers for support, I'm sorry that you feel it hasn't helped.
I don't know if it is any consolation, but please know that you are not alone in what you are going through. Many people struggle with fitting in at high school, feeling like they are constantly judged, bullied, ignored and/or excluded. People can be really horrible to each other for all sorts of reasons. It is also important to remember that sometimes things are not always as they seem from the outside - people may look like they are "in" the group, but internally may feel frightened, intimidated, powerless or anxious (but just be very good at hiding it or projecting it onto others and hurting them in the process). Peer pressure is another problem which can dissuade people from breaking from the group and inviting someone new in. Please don't feel that your career depends on the friendships you make with people in high school though. There are so many other opportunities to meet people, I know it feels so important right now and hard to see, but please know that what you do once you've finished school and how you achieve that is not dependent on who you make friends with. It can feel so lonely when everyone is already in groups and knows each other from before, it can be depressing and make you feel like an outlier. But as you have mentioned, you can meet new people and you don't have to do things you're not comfortable with in order to fit in. Focus on what you enjoy maybe join a debating team or find a group outside of school that interests you, give yourself the time and the space to adjust to the changes that are happening and seek support if you need to. There are some great resources available on https://au.reachout.com/ for young people that I would encourage you to have a look at if you are open to it.
Please do not hesitate to reach out again, we are here for you. Take care.