I think you may be missing my point about the secondary moderns unquietdad. If a grammar school creams of the most gifted children (which they may not be so much as the most privileged but let that stand) then this is going to be to the detriment of all the other schools in the area. I have seen interesting researh which proves this if you don't buy the common sense argument.
As for your quotations:
'Of course, the grammar school system was perceived at the time as being very elitist and a force for not being very good for social mobility.'
Erm yes cos how many kids went to grammar school percentage wise again? And how many were not middle-class? Oh, and just remind me again how many kids didn't go to grammar schools. Ah, I see.
'It's rather ironic that it's actually turned out that some kids from low income backgrounds did benefit from that system.'
I've always agreed that a small minority of kids beat all the odds and benefited from grammar schools and I've always said shame about the many 100s who didn't.
'And probably that system got more people through from the bottom end of the system than we currently have today.'
How can that possibly be when we have a higher proportion of kids who a) stay at school till 16 b) leave school with qualifications c) go to university than ever before.
To argue that grammar schools somehow benefited the majority of kids is just silly.
I do agree that grammar schools are not the only problem in our education system though and there are other policies and schools which allow selection and which often mean that deprived families are v limited (to the worse-performing schools) in their choices.
As for Andrew Neil, I'm not even going to waste my typing on his views. And really using him as your 'evidence' of the value of grammar schools just confirms my opinion of them.