I'd just like to point out that although there are single-sex schools (and Universities in Japan), the vast majority of schools are co-educational, a practice adopted after the end of the war. I remember when I lived and studied in Japan and being quite intrigued by the schooling sytem consequently writing a paper studying the problems within it.
I remember in particular the effects of 'cramming' schools on pupils and the often intolerable pressures they would put on those preparing for university entrance exams. Also the phenomenon of bullying in Japan was often quite shocking...a symptom of the strict school culture in that pupils who stood out from the rest for some reason (too talented, not talented enough, looked different, less hygenic, too extrovert, too quiet etc) were often victimized, humiliated, and beaten just because of those facts and that they didn't 'fit in'.
Sometimes the bullying was instituted by teachers themselves, I remember one case where a schoolgirl was a few seconds late to school, and the teacher deliberately slammed the heavy metal main gate shut on her, crushing her skull. This was by no means an isolated incident. Murders and suicides were a problem, caused by both pupils' bullying and victimsation by teachers. Quite frankly the system could be quite ruthless at times. I'm not saying this was endemic, but it was certainly widespread.
What price success? I came across many school children who were mentally and physically scarred by the schooling system in both the single-sex and co-educational regimes. Also the education system emphasised teaching by rote, and the absorption of facts. University students had problems when studying overseas due to the analytical nature of courses in western institutions, thus tending to have problems producing critical pieces of work, and generally avoiding asking questions of lecturers and tutors as is the norm. I was frequently being asked to help Japanese friends with their essays, and tutors would often despair that they did not become more inlvolved in class discussions. Yes, they might have great mathematicians, engineers etc, but consider the price of that success.
Sargon