Quote from OP. "The policy actually says the ranking is based on "our assessment of" the predicted grades, which creates even more subjectivity."
See Cake's response "I understand where you are coming from OP, some schools give very optimistic GCSE predictions, others don't and pupils from the optimistic schools will receive offers based on grades they won't make" and won't need to as they only need to meet the minimum entrance requirements. And those at other schools exceed their predictions and end up with better results than those who received the offers but don't get a place.
So, guess what, some schools predict more optimistically than others and yet again, guess what, the school with the sixth form knows this and does something about it. And you call that "subjectivity". Seems to be one of your favourite words!
If for one nanosecond you could put yourself in the shoes of the Head of Sixth in this "up its own arse" school that you may or may not have a child whom you may or may not be interested in trying to get into, you might realise that he/she has a very difficult job.
He/she is going to be damned if he/she does and damned if he/she doesn't. This is why entrance exams are the only "objective" way of coping with this problem. But of course this obvious solution is not allowed.
So the poor Head of Sixth, (and I am actually beginning to feel a bit sorry for this person now), has to deal with predicted grades from a range of schools, some of which may be accurate and some of which may not. He/She is hidebound by the law on Admissions Code so dare not put a foot wrong while at the same time being forced to be fair and to be SEEN to be fair in allocating places.
So he/she, going by the track record of predicted grades from schools in the area, allocates offers to students according to their predicted GCSE grades. At the end of the day, what is this person doing wrong? We already know that once the place is offered the offer cannot be withdrawn unless "it is established that the offer was obtained through a fraudulent or intentionally misleading application." (Quote from the Admissions Code). So basically He/She has one chance to get it right based on fairly dodgy info.
I actually do get it. I may be the only person on this forum who does get it, but the school and the governors must get it too.
As I said a long way up the thread, if you have a child and if he/she needs to get into this school, then you have little choice but to play the game. If they don't get in then trying to get them in on some form of technicality is a hiding to nothing. They either deserve a place or they don't. Better to spend the time ensuring they get the grades than farting about with all this stuff. (End of rant).