Katharine. When you have 850 young healthy males cooped up, with very limited contact with the real world I suggest that any attractive female would be a major distraction. There is one member of this forum whose inward letters from a female had to be examined by his housemaster in advance of his reading them in the housemaster's office because of the restrictions - the was not his mother1.
As for my own experience of female teachers there were only two. Miss Welch, my primary school teacher, loved rapping knuckles with a ruler and I got it hard because I started off left-handed which was totally unacceptable.
The second was a CH Horsham teacher. A large sheet of paper in front of each of us and told "paint". I for one, had never even seen a painting, I didn't even know what a painting was and she gave d**n all instruction. Stupid cow. Years later when doing A levels I suffered her again; I found that I could do very good drawings of human body parts (those NOT normally clothed). I could probably do hands blindfold, I did so many it was a waste of time. I now have the opportunity but she has so terrified me that I simply cannot bring myself to get the stuff out of the drawer beside me.
So, Katharine, I have little doubt that there are good female teachers - possibly better than the male teachers I see around here but I would not use that descriptor about my grandson's teachers.