My dc attend a grammar, not independent, school, but in all fairness I can see that it gives them an advantage.
Their peers are generally highly academic and ambitious. They encourage each other, in their group, to aim high - and have a healthy competition to do so.
My older dcs experience in (well regarded) state primaries was mainly one of an undercurrent of bullying for being a 'nerd' and 'swot' and they were, frankly, not entirely comfortable with aiming high and working hard.
Ds1 is on a whatsapp group where the older boys in his school are offering advice and information on applications to courses such as Medicine, for example. Would that happen to the same degree in an 'ordinary' comprehensive school?
He recently attended a course at Cambridge Uni (emphasis is attended a course - he is not at Cambridge
) and he and a friend had been chatting on social media with boys in their year about the different colleges at the Uni and their respective merits, so they decided to go and see a particular college that they were interested in.
When they got there, it was locked up and there was little opportunity to really look around, so they were about to go when a student there recognised ds1 and called out to him - he'd been an ex-pupil at his school. He showed both boys around the whole college and had a great chat with them about the application process - he happened to be doing the same course that Ds1 was interested in. Again - is this likely to happen to a pupil from an ordinary comprehensive?
I am not gloating about the fact that dc are in schools where things are made easier and doors are (literally) opened for them. But I am noticing it.
When ds1 was small (cute) and 11 years old and I was waiting for his 11 Plus results, the main hope I had was that he would be in a school where he was happy and comfortable, and for his personality and needs, that had meant a selective grammar. I have since realised that it means so much more than that for him and I am still grateful for that moment, 6 years ago, when he was offered his place.