I suspect IM that the reason the parents like it for their bright kids is because they have been offered a place! the perceived wisdom with GS and SS GS is that they are the right
school for the child because they have scored enough to be offered a place.... circular i am afraid.
When I was 11 (
a very long time ago) I lived in Solihull where there were 3 possible GS for girls, places , I think, offered on score (who knows .. not much was ever said...
There was a distinct "pecking order" - 1) Malvern Hall, 2) Tudor Grange, 3) Harold Cartwright... the majority of parents put them in that order and the girls who passed were given places which ultimately confirmed the order ie MH did better then TG which did better than HC.... rare for parents who had a kids capable of MH who decided to put HC first , would have felt they weren't doing the "right thing" ?? Maybe something similar is happening in people going for Pate's?