When I saw the topic of the debate, I immediately jumped on it to comment. However, it was as though Abod took the words right out of my mouth!
Yes, earlier on, girls and boys can, and should be in the same class, as they are more likely to form healthy, not disastrous, relationships with each other. It's during their teens that things can go wrong, and they should be separated for their own good, due to their raging hormones...
I've seen a lot of this in the co-ed schools in my own country. However, they can be in the same classes later on, when they're a little more mature.