Actually, I had the experience of both.
I attended high school in a region that did precisely just this thing.
My freshman and sophomore years were spent in a "girls only" high school. It was a new school, and still under construction those two years, but I think there was a very free atmosphere during that time. Granted, I don't know if that was due to the students, or the lack of anxiety of the staff, but I personally felt I learned more during that time. (Dress codes, etc? Forget it--no need.)
When they integrated the boys during my junior year--um, I actually felt sorry for the boys.
I recall, distinctly, a friend of mine, leaning up against the wall outside a stairwell, surveying the drooling adolescent boys, and saying, "I knew they were going to send boys--but did they have to send us boys?"
Um, y'see, we'd grown accustomed to skipping out with the construction workers.
We wished 'the boys' would go back to the apparent armpit that spawned them.
But that was just my experience, and not necessarily a reflection of the opinions of the management.