"Schools are oversubscribed - areas are not. Oversubscribed schools tend to be the ones with good Ofsted ratings and results."
That's not the full picture.
Schools with good GCSE results will be oversubscribed, period, regardless of the OFSTED ratings.
For example, Newport Free Grammar School, gets some of the best GCSE results, for a comp, in Essex. It got 575 applicants for 168 places, and nobody outside catchment was admitted.
Fully half of the cohort comes in above level 4 at age 11, and their 2012 performance of 65% good GCSEs is very mediocre considering.
www.education.gov.uk/cgi-bin/schools/performance/school.pl?urn=115352
Meanwhile Clacton County High School, which got only 425 applicants for 279 places, and comes near the bottom of Essex's GCSE league tables with around 50% getting 5 good GCSEs, actually gets objectively better results.
In particular:
CCHS - 66% made expected progress in English
NFGS - 61% made expected progress in English
The average GCSE grade was the same for all three (those with Level 3 or below at admission, those with Level 4, and those above Level 5) categories at both schools.
In many respects the 'poor school' got better results, it's just hamstrung by its intake.
And since those data were published, CCHS made a huge improvement, from 51% getting 5 good GCSEs in 2012, to 66% this year.
As for Ofsted, it was rated Grade 3 (the second-lowest) in 2009 and again in 2012, resulting in the head in 2012 resigning, and quite rightly so, because their results are plainly abject, as noted here: dashboard.ofsted.gov.uk/dash.php?urn=138734
Despite this, a former Ofsted inspector still complained about the report, saying that the outstanding GCSE results (which are actually anything but, due to the nature of the intake) are all the vindication that the school needs.
CCHS btw was rated 'Good with Oustanding Features'.
The point is this: first and foremost parents want good GCSE results. They pick the schools with the highest % of GCSE passes and that's pretty much it.
In most cases they are simply selecting the school with the most exclusive intake.
You get exceptions, such as Mossbourne in Hackney, where schools have managed to transcend their intakes and achieve well, and subsequently become sought after, but this is much less likely to happen in the shires.
The top comprehensive in Hampshire, Thornden has 56% of its intake at Level 5 or above on admission, and only 5% below Level 4. The worst, Mill Chase, has 25% and 22% respectively.
In Surrey it's the same, the top comp (which is actually a private school in disguise), Gordon's took in 58% at Level 5 and above, 3% below Level 4, the worst, a few miles away, Bishop David Brown, comparatively 19% and 28% respectively.
The problem is that 'good' schools create bad schools.
In the case of Newport Free Grammar above, it is one of four schools in Uttlesford:
Mountitchet, which is undersubscribed and gets 'poor' results, gets 23% high achievers, 25% low achievers.
Newport Free Grammar, which is heavily oversubscribed and gets 'good' results (but are actually well below par for its intake) gets 49% high achievers, 8% low achivers
Helena Romanes, which is full but not massively oversubscribed, and gets 'good' results, though historically not as good as NFGS', gets 38% high achievers, 12% low achievers.
Saffron Walden, which tops the Essex league tables every year, and is oversubscribed, gets 55% high achievers, 5% low achievers.
The top 3 schools take 311 high achievers and only 52 low achievers, while the bottom school had just 17 high achievers and 19 low achievers.
A small number of low achieving students will get into the 'best' 'comprehensives', but the 'worst' comprehensives will get very few high achievers, because those high achievers are, at elast in part a product of their home environment, which in most cases will do whatever is necessary to avoid a bad school.