Being nervous when you start high school is totally normal.
I was pretty worried when I started high school because I had previously been to a small middle school where everyone knew each other and it was a tight-knit community (most of us are still Facebook friends to this day).
But almost all my classmates went to one high school, and I went to a different one across town...
It was no fun at first, I was the "new kid" and even though lots of people were nice to me, it still felt strange not knowing anyone's name, or where my classes were.
But after a few days I got to know people and work my way around - and life was "normal" very quickly.
Sure, there were ups and downs throughout my time at that high school... But that's the same for life in general. And looking back at it, I had some really great times there and made loads of news friends.
Hopefully that reassures you a bit! But if you want to discuss specific things you're worried about in more detail, feel free to comment below!