@FlatStanley50 @Hotdoughnut the social aspect really isn't a worry.
As I said, DD's longest friendship group is with mainly Asians (mainly Muslim).
Although they don't get to go to town, they do have parties, they do go to dinners in town, they do have the girls over to theirs.
To be honest, the first few years is very heavily parent dependent anyway, as most girls don't live down the same road, or even the same estate, heck - not even the same town. So whilst they are young, the parents do take and collect them from get togethers.
It is also essential to note, that a huge change to friendship groups happens when they begin Yr10 and are put into groups where they mainly mingle with those who've chosen the same options as them. This is a huge change, and leads to solidifying of some friendships and new groups forming.
DD is still friends with her initial group, but now goes out regularly with others. They can meet in town, now they are old enough to navigate transport alone and they have sleepovers.
I'm genuinely really happy that DD is at a single sex school. She still has some male friends, but she is not distracted by boys, not distracted by heartbreak and is not sexually harassed.
I'm biased as I was sexually harassed as a teen (actually from 11), due to the fact that I developed young, it was awful at school, awful at home.
It affected my schooling. Boyfriends affected my schooling. I was unusual, I know, and my experience was different to most. But DD also developed young, and has no pressure to look a certain way, be compared to other girls, plus she can excel in Maths and Physics, without having sniggering or intimidation from boys. Again I experienced this.
DS went to the Grammar. I kind of wish he'd gone to SHFGS (he was autistic and not very sporty). This did worry me when DD chose AHS, but she's happy with her choice, so am I.
AHS is wonderful at supporting students and they are not as pressured as you may believe. They really do support pupils, even if they struggle, so don't worry about them not being able to keep up, it is not a hothouse, where they push for the results they get. It's more, the girls want to do well.