Nonsense. I went to an all girls prep school. Almost everyone I knew who went to Catholic high schools went to single sex schools. The tomboys, the nerds, the Barbie-dolls, all did well. I don't understand this aversion to single sex schools. Especially at the high school level, girls in single sex schools don't have the boys to worry about and it allows them to concentrate on their school work, activities, and to have leadership positions they might not have (or they might not want because of how they want to appear before the boys) in a coed environment.
As for boys, 4 years with the Jesuits (who aren't afraid to use corporal punishment) or in a Christian Brothers school will keep most boys on the straight and narrow.
The idea that kids in single sex schools won't know how to interact with the opposite sex doesn't make sense. People have brothers and sisters, kids go to camp, Sunday school, etc. and have plenty of opportunities to interact with the opposite sex.
What they are in school to do is to learn and study. Taking away the immediate distractions of the opposite sex, especially at the high school level, allows them to do that.
i agree with you completely. i think people have a certain idea of what all boy/all girl schools must be like, and have never been inside one, or known anyone attending a single sex institution. they’re just like mixed sex schools. only better : )