Arisbottle "I am against grammar schools because I know they are there to keep the unwashed dirty and distant."
They weren't designed to do that - quite the reverse. They were designed to make sure that bright children had the chance to access a free academic education, regardless of background.
I think the main reason why this is no longer the case is that state primary schools don't now regard it as within their remit to encourage or prepare children to take the 11+. They do not make it their business to ensure that all the relevant parts of the syllabus have been covered, bearing in mind that where the 11+ includes maths and english papers, children taking the exam (start of Yr. 6) need to be familiar with the whole KS2 syllabus (end of Yr. 6 in most state primaries).
That is where the rich/poor split comes in. It is not that the poor have less interest in, or aspirations concerning the education of their children, but that they cannot access private schools, which will teach to the 11+, or tutoring, which will plug the gaps that the state schools leave.
When I took the 11+, everyone sat the exam, in their own school, and it was a raw I.Q. test - I'm assuming verbal and non-verbal reasoning. We had done a couple of practice papers - everyone - rich, poor, bright, average. Tuition was unheard of. Whether you approve of selection or not, at least that was a system of selection that was open to all.
The problem with grammars nowadays is that they are essentially out on a limb within a largely comprehensive system. State primaries have distanced themselves from the whole process, even where they are the feeder schools, thus preventing many poorer children from accessing the help and encouragement afforded to those who can pay.