Single sex (state) schools do not exist where I grew up (Switzerland) so the question never arose. I think I would have just hated it...
Our girls in the UK went to co-head schools, mainly because this is what was available locally and because of the 'sociall well adjusted element' you mention. However- DD1 was extremely bright abd loved science and wanted to become a vet. The elderly man who taught physics and chemistry at the high school (10-14) she attended was very old fashioned- and would totally ignore the girls in lessons. We did persuade her to volunteer more, put her hand up ... but to no avail. We gently talked to him at parents' evenings- but it was like talking to a wall. And it did put her off. She did chose chemistry, physics and biology for A'Levels- and was put off by being one of 2 girls in her classes, and feeling she had absolutely nothing in common with the boys in those classes. She got glandular fever and dropped out of physics and chemistry and swapped mid year for art and French, against all advice. At that time, I felt she would have probably been much better off in a single sex school. She did extremely well at Uni and in her career anyhow- but she probably would be a vet now had she gone to single sex school (which may or may not have been better than her current career- certainly very different).
I did teach in a single sex school at the beginning of my teaching career - and what you describe was a common occurence. The boy's school was next door- and our girls were forever hanging out of the windows to oggle the boys in the sports ground, and vice-versa! Bike sheds in between the two had to be very closely supervised!!! They were obsessed - and it did make me think it was not healthy.
OH went to a single sex grammar school (Woking Grammar)- and he used to tell me how obsessed they were with the girls, and vice-versa- and how they always tried to go xcountry running where they could catch a glimpse of girls in gymslips!