Look - why is selection by parental income such a massive issue for the pro-grammar brigade when it comes to comprehensives, but not when it comes to grammar, where it is VASTLY more of a problem!
Poor children are hugely under represented at grammars and dealing with the problem is proving intractable.
Comprehensives on the other hand are starting to get around the challenges of unfair access by introducing lotteries and fair banding. They aren't the whole answer to the problem but can make a very significant difference.
However, I think this issue of access for poor and low achieving children to any 'good school' is fundamentally difficult, given that intake is part of what parents feel makes a school desirable or otherwise.