Look, I was in a similar situation last year and ended up going to the Grammar Sixth Form, and I hate it so much, it's not my type of school, it's quite a independent and well behaved place, in general I'm not used to so much, and still am not. I also go to all girls grammar, although there are links to the boys school I don't think it's the same. But if you think it's right for you, go there and have fun, make friends and try to enjoy it more than me 😉
Anymore questions feel free to ask