I am a great believer in single sex education.
Not because I believe girls learn differently to boys, but because I think they are treated differently to each other in a school environment (as well as in every other environment......).
DD1 is at a girls grammar. She is a bit geeky, TBH, and that's fine, because so are her friends. Even so, she is on good terms with almost all the girls in her class, and will chat to them, socially.
As far as socialising with boys is concerned, she has never wanted to go to the school discos where boys from the nearby boys' grammar are invited, although lots of the girls do. She travels on the train to school, and they often sit with boys from the boys' Grammar. She also has a few hobbies where she meets boys, and I can see friendships with some of them forming in the next year or so.
I went to a coed, and was bullied by boys and girls alike. There was no shortage of bitchiness, if that is what you want to call nastiness when performed by girls.
At the equivalent of A level, at my school, I was one of three girls studying the equivalent of further maths, in a class of about 20. There were two girls studying physics. At the nearby girls' school, they had full classes of these subjects. On the other hand, there was one boy in my English Literature class, of about 20.