Personally as a parent of a younger child my own yardstick of local secondary schools has been the behaviour of the kids over the years around and about . I can honestly say that that of the Sydenham Girls in the town centre has been mostly appalling, at least of the few who seem to tar the rest with the same brush. I overheard some girls on the phone at the station to another girl threatening to kill her if she came to school. I managed to work out a few of the girls names so called the school shortly afterwards to complain and report this. The schools response was so disinterested that it was hardly there, ie what do you expect, girls will be girls, etc. hormones and all that. They probably didn't even investigate.
If that's the standard then its understandable that the girls behaviour is what it is. I most definitely will not be sending my daughter there.

Having visited FH boys school, and met some of the children and their teachers, I have found little to complain about.

Unfortunately first impressions, even superficial ones, last a long time.