Well I'm a middle-class parent who went to private school, but I still dont understand this GS obsession?
My oldest didnt take the 11+ because she knew which school she wanted to go to; 2nd one did take it - simply because she wanted to - but did not pass (no tutoring, no downloaded papers) but they are both vvv happy at their secondary modern.
There is absolutely NO understanding that grade predictions are what they aim for, all their teachers use them as a base point rather than a target.
What I find interesting is talking to their GS friends, because they seem to find their lessons much less interesting, much more teaching to the exam etc, whereas my 'less academic' two are much more able to explore a subject in depth...