No system is perfect or 100% fair...at least around here you can't buy your way into a leafy comp just because you can afford the inflated house prices within its catchment...how fair is that?
Around here the grammars have virtually no catchment, some pupils travel in from 20 miles away. Absolutely all manner of housing stock is included from a sink council estate to rural, period mansions and everything in between.
Some parents pay for tutoring, but not most, probably because there just aren't the numbers of tutors available. And yes, we paid, so you could argue that we had an unfair financial advantage.
But even if we hadn't paid for tutoring, our DDs would still have had an 'unfair' advantage being born to graduate parents. Being exposed to more sophisticated vocabulary. Growing up in a house full of books etc.
If there actually is the occasional very intelligent child, whose parents are somehow totally illiterate, who don't even have a roof over their heads where their child can sit in a chair and look through past papers (so they're living on the streets?)...if their parents are so disengaged that they don't even know of the 11+...then really whether this, supposed, child can/can't pass the 11+ is a bit of a moot point, really.
Because even if they passed, their parents sound like they'd be totally unable to provide them with uniform, stationery, sports kit, bus fares...
So angst-ing over the 'unfairness' of them not sitting the test seems a bit pointless?
No system is perfect...and for every unfortunate child who did have the high IQ to pass the 11+, but wasn't supported properly by their parents...there is a similar, unfortunate child, with the same high IQ getting bullied at their comprehensive for being a swot...