If it's any consolation, I'm in a similar situation to you right now, but I'm starting my first year at uni rather than secondary school. It's terrifying, I'm nervous about it and very very anxious, but it's a new stage of my life and I accept that it's going to be daunting at first but things will settle and I will find a new normal amidst the anxiety and chaos. You will get used to it. The first few weeks will be scary but you will settle. Everyone is going to be feeling the same as you, they will be afraid and nervous and anxious starting in a new school with new people. The best thing to do is to be positive about the whole experience - easier said than done. If you smile, you chat to other people, try your best to make a good impression, you act friendly and kindly to other people, then you have nothing to worry about. Just actively go out there and do stuff to get to know new people. If you see someone sitting on their own, go up to them and ask "is it okay if I sit here?" and just sit right next to them and get chatting!
Likewise, with school work, admittedly, high school is not too bad work load wise when you're in your first year, so don't panic about it too much (going from my own experiences here in the UK though so might be slightly different). For me I am never worried about lessons and homework and stuff because I know I'm very academically disciplined so I can work to deadlines with ease and I will study independently. But at the same time if that's something you struggle with then get organised now. Get a diary or planner and write out to do lists of everything you want to do in the evening you get home from school, write down assignment dates, how many days you have to complete things, plan out your evenings so you know what you need to do when you get home. I find that really motivates me a lot more and it actually makes sure I do something productive.
Overall, just try to stay calm and positive. Like I said, it's easier said than done, but this feeling WILL pass. You will get through this and survive it. It may not be fun or enjoyable during those first few weeks but you will settle and get used to things, and then you'll reach a point where you can't really imagine your life being any other way.
To tell you the truth I'm incredibly nervous at the moment too, because I'm moving away and doing something completely new and different and I'm really moving out of my comfort zone. But sometimes doing scary things can end with the best results. So you just need to be brave and embrace your school life as much as you can, because before you know it it will be over. So try to make good memories, even if school can be kind of bad at times.
