I was originally going to a girl's school mixed sixth form until a few months ago, but luckily I found another sixth form (a mixed sixth form of a boys school). Thank god I'm going there, I would be ****ed otherwise. Maybe I'm not being very helpful but my point is, as long as you're a social king/lord, you'll be fine. Don't expect people to talk to you, just try to talk to others and you'll be alright. My advice is make sure you do get friends as otherwise you'll be miserable during A levels, which you don't want.