This happened to me during sixth form. Had no friends for those 2 years. It is depressing, but the only alternative is trying to force yourself into another friendship group which I found too difficult. I don't know how confident you are, but I can almost guarantee you are more confident than me you'll probably make friends eventually if you talk to people in lessons.
However, if you don't make friends, then just make sure you get good grades. I got good grades so now I don't regret choosing my sixth form.