Sorry but I really don't.
I just think it's crazy to separate people based on gender, you would never do the same thing with race for instance, so why gender?
I admit I don't have much experience with single sex schools, I went to a coed school like most people did and I loved spending time with both boys and girls whilst I was in school. I don't think I'd have had the same experience or enjoyed it anywhere near as much if it had just been all girls.
Do people who go to single sex schools tend to find they have trouble mixing with the opposite gender later in life? The working world isn't single sex so why should school be?