That is true enough, but there's no doubt (only from what the admissions officer told me!) that there do seem to be a lot more prep DCs applying at the comps this year. But there's a reason why Winchester doesn't have any middle of the road private secondaries, I suppose (ie not Winchester College or St Swithun's), but I've heard from a few hospital consultants that there's a lot less talk about 'King Eddy's' (private selective ex-grammar in Southampton with v. good results) than in previous years!
Now, I actually agree that in some ways, going private DOES potentially deprive a local state school of nice, middle class DCs from nice homes- perhaps not so much the case in Winchester where EVERYONE is middle-class (!)- it's just that I recognise that DC's in my DS's position will, sadly, have his chance of attending one of these excellent comps reduced.
It kind of goes to the heart of the inequality issues that increasingly dog our country, really. When we're in clover, the wealthy can desert our state schools which, in the case of the schools I'm talking about, get on with it, achieving excellent results and turning out a 'high quality product' (if you'll excuse the term!), but when the good times falter, the wealthy by dint of their house purchasing power, can mob the good state schools and thus further reduce the chances of the less well off.
It's a fact of life, I know.