Gender is important in school choices but it is not as simple as it may seem.
Diamond model schools (Co-ed junior, 2 single-sex sections to age 16, co-ed sixth form)
Berkhamsted School
Brentwood
Claires Court
Clifton High
Dame Allan's Boys' & Girls'
Forest
Grammar School at Leeds (GSAL)
King's (Macclesfield)
Mary Erskine (& Stewart's Melville)
New Hall
Oldham Hulme Grammar
Stewart's Melville (& Mary Erskine)
Stover
Teesside High
So what are the arguments?
Then there is the detail. Some single-sex schools have a range of activities with other schools, so pupils can play in orchestras, take part in debates and outings etc with pupils of the opposite sex; others are, perhaps depressingly, isolated. Schools that have recently become co-educational should be looked at carefully to see that they have done so successfully. To do this successfully requires considerable adjustments, not only to the physical environment but to the social structures, sports offered and school ethos. Some schools manage this better than others.
In practice – as so often – different approaches will suit different children.