I went to private for both primary and secondary and my primary school was ok, but it was a big commute so we went more local for secondary. My mum feels i was neglected at the secondary school, I was bullied relentlessly, once nearly having my arm broken, self harming etc. It was very focused on academia, with not much in the way of pastoral care. When my mum had a meeting with my form tutor, she admitted "Well to be honest with you cadbury is such a good girl I've ignored her for most of the year".
They did a GCSE certificates presentation evening and in the info/leaflet they gave out to everyone it listed every pupil's name and how many As/A*s they got. I knew then I'd made the right decision to leave for a state sixth form!
As for grades, I was a "middle kid". I did ok at GCSE, not amazing but I struggled with maths so managed to scrape a pass. I benefitted from the leg up, I think. With regards to my friends I made there, some of whom got straight As, but there is still a mix of careers - doctor, vet, SAHM, occupational therapist, travel agent, entry level office worker, academic, museum curator, varying grades of office worker.
I agree with whoever said it is the right school for the child and that you can't buy grades.
We cannot afford private education for our DC so it is not something we are thinking about. My friend who is a doctor is married to a solicitor and they are not sure they will be able to afford private education. Back when I was in school, most of my friends' mums were SAHMs and their dads were in good careers, but they managed to pay for school fees for 2-3 children. That world has changed.