Custy - sorry I am a bit confused. For us it would be a choice to move, partly because DS could end up being one of the ones with no school place in the borough - fine if the place that is found is within easy travelling distace, not fine if it is an hours unreliable bus service away(which wouldn't imply choice at all).
Actually, some of the lambeth 2ndry schools are good, and getting better - and a new one will be built in Brixton within the next 5 years.
Lambeth is a long, thin straggly shaped borough, and has 5 other boroughs bordering it - so convenient schools can easily be just across the border.
RE thew Observer article: I was a bit confused by the pov of some of the parents there - One mother and son were talking about it being a problem that he didn't get into the Lambeth Academy, but 'had' to go to Dunraven instead. Dunraven is an excellent school (foundation, takes equal numbers of kids from each of 5 ability bands) and v v close for anyone attending Sudbourne.
Also Sudbourne Parents! The cheek of it! Don't know about those individuals, of course, but Sudbourne is absolutely colonised by people who have rented houses on the doorstep for a year (and then sublet them) in order to get in. Or have knocked on doors offering money for the use of an address - all documented! We would be in the natural Sudbourne catchment (we are 7 minutes walk away) if it wasn't for all that!
I think the other big problem with admissions and lack of offers is that the wonderful Capita are in charge of the system.
So, yes, there is a problem, and a big problem, but I don't think it is EXACTLY as described in the Observer. And here many are of Lambeth Councils making, rather than Blairs. (oooh, how it grates to have to suggest that!)