This is a legal ruling and applies everywhere.
Greenwich Judgement (1989)
This judgement established that maintained schools may not give priority to children for the sole reason that they live within the LA’s administrative boundaries.
Rotherham Judgement (1997)
This established that admission authorities may operate specified catchment areas as part of their oversubscription criteria provided that, in doing so, they are not in breach of the Greenwich judgement.
So there are methods like catchment areas which can be used, so long as it does not contravene the Greenwich Judgement.
Dartford Grammar offer to those parishes within Dartford first, then to OOC
I think Dartford manages to remain within the admission code, as the criteria before parishes, is a one mile radius around the school - which I believe includes Bexley. This does seem to be a token offering as the area in question is described as - not particularly residential and not likely to yield many places.
The adjudication from 2009 can be found here