I have lived in Knutsford for 40 years and attended Knutsford Comprehensive before it became an Academy, as did my wife. My two sons (both near the top of their respective years academically) are current pupils, and many of the brightest and best from their very highly rated primary school also attend.
The second hand information from the individual 270 miles away and who has no knowledge other than that obtained by anecdote from their brother (who presumably didn't attend and therefore is relying upon dinner party chit-chat) is just that, second hand.
Of course there is a significant percentage of the population of Knutsford who send their children to private schools but that is true of almost any area as wealthy as Knutsford.
The Academy has had a huge amount of money invested, is promoting extensive use of and education in IT (yes, programming not how to use applications) and has an excellent pastoral care system.
The staff have, for the last 10 years at least, been highly motivated and dedicated and it is worth noting that some staff only recently retired were my teachers in the late seventies and early eighties.
Yes, pupils from other areas are bused in, but that is because the state schools in their own areas cannot compete with Knutsford Academy.
And finally I would point out that not only did I have a private education in Worcestershire to the age of fourteen before attending the school, but we could easily afford to send our boys to almost any private school.
My comments come from genuine experience of both systems of education and personal experience of the school.