Actually seeker, they could well be 'worse served'. And that does not, in any way, mean that i think a high IQ is that precious and fragile that it cannot be touched by someone with less 
Your determined refusal to see that comprehensives are not the educational holy grail is astounding.
You have been given an example of an outstanding comp that gets less than a handful of A*s. As per the point you keep making, this is not because children from lower income families do not have natural intelligence.
It has been pointed out that comprehensives can and do struggle to truly stretch the most able students because resources need to be targeted at those struggling, or those on the borderline between a C and a D.
You refuse to admit that peer pressure and a negative attitude towards education can have a detrimental effect on some children. Why is that? It can and does happen.
Why is it that you think the non grammar school children will benefit that much from being educated under the same roof as grammar children? As you say, they will be in different sets anyway.
I don't understand why you think that something the benefits children should be taken away from them.
What is it that they have to offer others that makes it so essential for them to all be together?