Boys and girls

I've noticed that in Japan the genders tend to be somewhat segregated. Guys and girls don't seem to hang out in mixed company as friends in the same way or with the same frequency as in the States. They don't tend to mix unless romantically involved or thrown together circumstantially (a circle, club, organization, etc.). Of course I'm generalizing, but the difference from back home is noticeable.

The effects of this behavior sometimes spill over into the classroom. Of course there are boys and girls who are friends and who have no problem talking to each other or joking around. Sometimes, though, I've noticed when doing pair work some co-ed couples have trouble. Today, for example, the students were practicing a dialogue in pairs. They were told to partner up with the student next to them. Two pairs of boys and girls wound up partnered, and they didn't seem to know how to handle it. I noticed them just sitting there, looking shyly at their papers and not speaking to each other. I went over and asked them in Japanese what was wrong. None of them answered - all they could do was look at me (the boys managed to smile coyly). I wound up rearranging them so the two boys were paired as were the two girls. Problem solved.

Still, seems rather silly to me. I went to an all-boys high school, so I can't exactly relate, but I don't remember having any problems talking to girls in class before or after that. Is this a common phenomenon in other countries, or just here?