I go to a private school and personally I wouldn’t change it for the world. Teachers are genuinely invested in you, not only your education but how you develop as a person. You’ll find that you make friends there but during the holidays you won’t interact with them as you’ll be home/needing a break from each other so you’ll have plenty of time interact with your old friends. I’m not a boarder but at my school, day pupils can board 1 a week for free, and stay till 9 each day, and in sixth form we have our own rooms even as day pupils. I find boarding life to be good and fulfilling and will really help prep you for university. It’s a scary step but unless you really really wouldn’t want to be away from home, any nervous feels will settle quickly.