A selective system should/needs to take in to account bright children with Dyspraxia/Dyslexia Aspergers . These kids who may struggle in certain areas, but given the right help and equipment would benefit massively from a grammar school. These are the children who perhaps need a focused disciplined environment more than bright pupils without their needs
And this ^^ is exactly why we have opted to send our 10yo DS to a small, nurturing, SEN-supportive private school when he starts Y7 next year.
We had a place at our local comprehensive for him. Local comp is a brilliant school, highly regarded, great results. But big. Around 1,500 pupils. Not a great reputation for SEN support, particularly not for kids like DS who has Aspergers/ADHD but no associated learning difficulties, is quite middle of the road academically and has no behaviour issues. By which I mean he's not going to 'stand out' as needing support or causing staff any problems but could flounder and struggle emotionally and get a bit lost in the system.
And I have read too many posts from SEN parents whose ASD children are having a really rough time in the comprehensive system with little or no support. So - the private school with small classes and SEN supportive staff it is.
Like others I find it massively offensive that people make the 'rich and thick' assumption - just as I find it massively offensive that people refer to comp children as spending half the day chucking chairs around.
DS is bright, bright enough to pass the exam to the selective independent school we had (very carefully) chosen. But probably not bright enough for many of the selective grammars. So in our case, to answer the original question, even if grammars were available in our area we would still be going down the private school route for DS1 because neither a grammar nor a huge comprehensive would really be right for him. We are very lucky that we are able to pay for what we feel is the right school. Just as other families are very lucky if they have children who are academically able and socially sophisticated enough to breeze through the state system and achieve highly without the need for any additional help.