I went to an all male High School and we had plenty of contact with girls, it just wasn't at school, except for the huge dances our school would throw. I'm sure we "acted out", it just wasn't during school time.
While I do agree that kids would come into contact with the opposite sex at times, those times could be few and far between. In some family settings they could be quite minimal.
You may disagree with me, but this is a scenario where boys and girls don’t get much face time in social settings until after high school. Then they are sent off to co-educational dorms and the sudden shock of doing anything they please while still social children.
This seems like a recipe for disaster to me.