Colleger,
My 'oddest group' is definitely mathematicians. Lovely, in the main, but quite startlingly odd - though where i know the whole family the families are mostly [I exclude the family in which ALL the family members, male and female, for the last 3 generations, are all mathematicians] entirely normal with entirely normal relationships within the family...
In those groups, I would suggest that it is the obsession with something quite abstract that is either a cause of, or a result of, the appearance of 'oddness' to others. Nothing at all related to education - all the brilliant mathematicians I know, male, female, young, old, from state co-eds and exclusive private boarding schools, are all equally a little other-worldly!
Thinking again about single sex schools, I do not, in the main, want or expect my children (or myself) to be defined by their gender. I therefore feel uncomfortable about an education which does so, somewhat as I would be about an education which divided them by e.g. hair colour, ethnicity etc. It seems to me important that they see role models and have friends and work alongside as wide a variety of others as possible - including both sexes.
However, I can see that IF in a co-ed school they were anyway being stereotyped by their gender ('boys run around a lot and don't work hard' / 'girls have neat writing so they are cleverer') then a single sex school might be the least worst option. However, in my experience so far, both of my children are being allowed by a co-ed education to think of themselves as 'learners' first and as girl / boy second, in a school where for a boy it is as cool to be top in maths as it is to captain the football team or play in the school concert, and where for a girl being the class's fastest runner is as valued as being a good artist.