In cities with plenty of schools (many just accross the street) the boys would go to one and the girls go to the other, entire buildings are separate. If class sizes are large then they are separated that way. No additional cost. There can be need. Horomones at that age run rampid, many girls and boys care more about what they look like to the opposite gender then about what is happening in class. Even gay kids have to worry about keeping up appearances as normally they are not at the age to fully understand their sexuality. I know that wile I was in high school I would have benefited from not being distracted with trying to get a guy home at lunch, and not looking stupid in gym class. I know may people who feel the same.
I suppose youd have to make it 'same sexual preference schooling' now, if you wanted to get the benefits that come from less distraction and lower teen birth numbers that come from traditional same sex schooling.
Stargate, I would agree with you except for the fact that there is inherent inequality amongst the sexes and sexualities. That they even come about at that young an age shows where their emphasis lies ... And its no longer on school or education.
So there you go ... Would a room of all boys benefit from being schooled by a male teacher who thinks the way they do and can teach more effectively to them? Same standards for level of learning at the end of the semester should apply ... But if you can improve methods and conveyance simply by changing the sexes of the individuals in the class ... Then I dont see a reason not to do it.