State primary schools do not prepare children for independent, highly selective schools. Many of the teachers thoroughly disapprove of such schools, but in any case its not what the state pays them to do.
The state pays schools to provide an "education", and there is lots of playing about with by politicians as to what that actually means in between reception and GCSEs, which are taken in year 11. However, a sort of minimum standard seemed to be 5 GCSEs at level C or better.
A "C" at GCSE was roughly equivalent to a level 7 on the national curriculum scale. (Now there is a new GCSE grading system as well as a new school grading system).
Taking the (now abandoned) NC levels, when they were current, the state system required schools to have pupils make 2 NC levels progress per key stage. Each NC level was 3 sublevels.
So, in the 4 years of KS2, the schools were required to have every pupil make 6 sublevels of progress (1.5 levels per year) , and from year 1 to year 11 inclusive, they were required to make 7*3=21 sublevels of progress (2.1 on average).
For some pupils, this was an incredibly low target. For others, it represented a slight challenge and for some, it would turn out to be impossible. In a mixed ability primary school, children from all these ability ranges sit together in one class, and each successive class teacher has to try to progress each of them.
The problem with the state system, IMHO, is that it is weighted towards the needs of the less able. This was exemplified in policies such as "no child left behind" and "every child counts" which were both about ensuring the least able met the minimum standard. In contrast, all extra funding to meet the needs of the most able was cut about 6 or 7 years ago.
For the most able, better than minimum performance is expected, but it really is the luck of the draw how much help you get to get there. You don't need much help to achieve a little higher, so even without any extra help, your child will probably get levels of attainment that will described as "good grades/ levels that others would love to get", even if they are nowhere near your child's potential.
Having your child reach their potential is the holy grail for parents of G&T children, but I've no idea how you can obtain help with that within the state sector (or indeed the independent sector - but only because I have no experience of it).
There may be a new measurement system but the objective of 5 reasonable GCSEs after 11 years of study still remains.
What i can tell you is that if you approach the meeting saying things like you say in your OP, you will only set the school up against you. From then on, you'll be treated to a (highly effective) combined strategy of kicking the can down the road and talking in double speak when good does not mean good and progress does not mean progress. All of this intersperced with hints that you are hot-housing, that you are not providing a rounded childhood, that you have a warped value system etc. etc.
Its not worth it.