We come back to the crux of the problem - there are some bad schools; and who would want their child to go there just because it was their catchment school?
Raising the standards of all schools is the way to go. There would then be no need to "cheat." How to achieve this? - I have no idea; except more money might help for better facilities, better support of new teachers, smaller classes etc.
It is a shame that parents judge schools by their OfSted rating. This was a little political game that was introduced so that parents could judge the "market" (groan) when what is really needed is the sort of school inspectors that also had a role as school support. If they found a weakness it was also their job to find a way of helping the school to eliminate it. Not as now where a weakness is just a downgrade that reduces the number of pupils wishing to go to that school and sets up a negative spiral.
Bollocks to the market principle being applied inappropriately!
To think that London, or anywhere else for that matter, does not belong to any one demographic