I have a 6 year old daughter in a Montessori school. After a class observation I noticed the teacher spent a significant portion of her time just dealing with a few rambunctious boys, while all the girls in the class worked quietly.

Afterwards, I asked the teacher why they just didn't separate the boys from the girls, since they were obviously two different species at that age (at all ages?) It seemed to me that a class with only girls in it could learn faster w/o all the silly distractions.

The teacher got quite serious and told me that girls and boys are a form of yin and yang. The classroom dynamic was an absolute necessity to the healthy social upbringing of each.