RosieWoodChelt,
My understanding is that your wish for boarding is, essentially, logistical and because you enjoyed this 'family tradition', and also that (for a reason you have not specified) that you think single sex education would suit your DD.
I don't get the impression that you know a lot about state education, because you move in 'private education only' social circles and your need for boarding because of your work and your DH's rules even the most astonishing state schools out.
Can iI therefore suggest that you don't make statements about state education at all? Of course, if you have visited all the selective and comprehensive options available to you locally, and have ruled them out individually as schools, you can comment about them in particular - e.g. you have not considered Pate's Grammar because you need your DD's to be looked after by the school at night and at the weekend, and it is a M-F day school, even though it is (in terms of academic results and progress) superior to the boarding schools discussed.
However, it does feel as if you have not spent much, if any, time considering or visiting state schools, and your sweeping statements do come across as both naive and a little rude. They may be 'the opinions of your equally state-ignorant social / educational circle', but it doesn't make them generally true.