I disagree about the impossibility of teachers teaching mixed ability classes of 30 in primary schools. Some schools in Wandsworth have amazing results with more mixed and challenging intakes than Ravenstone with children of all abilities making really impressive levels of progress.
If you are making the point that state primary schools do not teach to the test required to enter private secondary schools then yes, obviously not. It makes me laugh that this is considered so desirable in private schools when there is so much criticism of state schools teaching to the Y6 SATS test.
My eldest is in Y2 in an average Wandsworth state primary. I see very little difference between what she is doing and her peers in local private schools. I think it is a local myth that private schools are x years ahead of state schools.
There was very interesting recent research that showed that children do better at secondary school where they are higher ranked relative to their peers in their particular primary school (i.e., going to a school with overall lower attainment but where your child is at the top in terms of their attainment would appear to be better than going to the school with top attainment where your child is in the middle of the pack). I must admit that I haven't read the paper in detail (lots of complex maths in there!) but it says they analysed data for more than 2 million children and the hypothesis seems to be that the confidence that comes from being at the top has a significant impact (much more pronounced effect for boys).
http://cep.lse.ac.uk/pubs/download/dp1241.pdf
I also remember this article from the Guardian about children from middle class families suffering no disadvantage from going to poorly-performing state schools. To be honest, this is actually at the heart of this debate about Ravenstone, if your child is well-supported at home with well-educated parents, they will most likely do well at any school and so you may be more concerned about extra-curricular clubs and having a nice PTA. But, this is a bit of an uncomfortable truth because although many of our children will be fine, we still need to make sure our schools deliver for all children... Tricky stuff!
http://www.theguardian.com/education/20 ... schools.uk
Obviously, you've made up your mind medway but for anyone else, reveiw the facts, you may well conclude that your children CAN get the education you want for them at state school...