@LilacPoet I am sorry you are turning my enquiry into a personal attack, especially as you don't know about my personal circumstances. I am therefore ignoring your comments regarding what is inconvenient to me.
Regarding your other comments on the DGS admission policy, well, please let me point out to you again that 140 places (out of 190) are indeed ringfenced for local applicants (that is about three=quarter of all places). Even more, some very local students (i.e. living in the Bexley LA) fall out of the catchment area (as they are not in Kent), hence frankly this not so much about the local community (i.e. distance from the school) and more about protecting Kent students.
I am not arguing whether this is right or wrong (different people will have different views, mostly depending on how convenient it is to their personal circumstances), but it is a matter of fact (please read the admission criteria if you are still unsure).
As a result, DGS (or Kent Council) cannot claim that school places are allocated on the basis of score, when 'de facto' the most relevant admission criteria is whether or not applicants live within the catchment area.
Now, in this context, the School Admission Code would deem illegal the introduction of a sibling priority rule, hence I must assume that the school has chosen not to apply it.
Just for comparison purposes, in Bexley the top 180 scorers in the 11+ test are allocated a place in their own school of choice (out of the 4 grammars in that LA). That would be (on average) 45 places per school, which is comparable to the residual places left at DGS after taking care of the Zone A applicants. Well, all Bexley grammars have a sibling priority rule in their admission criteria, despite about 25% of places potentially allocated by ranking scores (very similar percentage to DGS).
That's all. As I said before, just trying to understand DGS ethos / objective in having such admission criteria, and whether they have considered adding the sibling rule (which would be allowed under the School Admission Code, for the reasons I explained above).