Can't sleep & spotted your post squeezedatbothends. I've written a lot here about this subject and am familiar with Guy Claxton (how wonderful to find someone else who's read the excellent 'What's The Point of School') and Carol Dweck's research. I am unusual in that I believe a minor intellect can become a major genius and that 'cells that glow together grow together' - in other words it is possible to become cognitively smarter with practice. As you say there have been developments in cognitive science too which seem to have passed most people by. We can get incrementally smarter, that's one reason I prefer to hear about 'current attainment' rather than 'ability' from teachers in primary schools. Intelligence isn't unitary it is about habits of mind which can be cultivated. Yet I think most still believe being intellectually superior or 'gifted' is something you are born with, will last a life time and is pre-determined just as eye or hair colour is pre-determined.
I also participated in the webchat with Matthew Syed - if anyone is interested it's probably still available on the site somewhere. I believe Matthew Syed is currently investigating 'ability' in schools, how it's spotted, how it's viewed and what the implications are. I will be very curious to see what he turns up.
I see all sorts of problems with our NC tracking system, it can mean that it's difficult for some children to go beyond their expectations (although I admit as a safeguard & check it generally does a good job). Claxton makes the point that once a child is generally seen as 'bright' by the teachers, they'll be treated as such and this can become a self fulfilling prophecy. If a child has been seen seen as 'slow' but their output improves in quality this is likely to be seen as result of their hard work rather than any improvement in cognitive ability. If a 'bright' child doesn't live up to early promise excuses tend to be found, lazy in with a bad crowd etc, but generally not that they may not have been so bright in the first place. As others have said there are also issues with being labelled bright, it isn't a helpful thing to do. Dweck points this out and squeezedatbothends I was like your son. I walked out of english S level as believed because I didn't understand the first question it wasn't for the likes of me, I must have reached my ability ceiling. Dweck's book literally changed my life and I think it should be compulsory reading for teachers, as should Guy's book. I had a fixed mindset but now I have a growth mindset, I have achieved more in my life since I read that book than ever before.
A dangerous teacher is one IMO who believes intelligence is fixed. Most seem to believe 'you've either got it or you haven't' and there isn't much anyone can do about it. Most assume intelligence is unitary, and can be accurately measured by an IQ or similar test. Most assume a seemingly high ability in a high status subject like maths or english means a child has a superior all round intellect. I worry that a poor performance in an early cognitive test administered by the school might mean that certain fixed beliefs about this child come into play. Sure, every teacher wants to see a child do well but it's human nature to label and make assumptions so we are likely at some level to assume the sky may not be the limit academically for this child. The same may be true for our level 4s at the end of KS2 for example. All the children that start ahead at our primary almost universally stay ahead, those that started ahead on the reading conveyor belt are now level 3A at the start of Y3 (Perhaps with one exception). Will the others catch them? Perhaps, but this group are perceived as very bright as they begin the new year which may give them some advantage in a class of 30 (although this isn't without it's flaws as others have said), not least sitting with children who are likely to be amongst the keenest in the class to learn. Not least because expectations are high. It's my view that an 'average' child with a lot of practice could be similarly accomplished. It's very dangerous to assume some children have less potential than others especially at an early stage yet I think we do on some level.
Claxton believes a 'gifted and talented' label is ok if we use it to mean a child currently surpasses it's peers in an area and should be encouraged to continue but it should never be used to mean 'possesses, all-round, high ability'.
All of this does not mean that there isn't some genetic component of 'intelligence' I like Claxton's analogy of intelligence in kitchen cooker terms (!) :):
Imagine that the genetic component of 'intelligence' is like the size of a kitchen cooker. Someone may have three cooking rings and single oven, and someone else has four rings and two ovens. These will set different hypothetic limits on the meals they can produce. But in practice, the quality, variety of their food generally reflects quite different things: how interested they are in cooking; the recipe books they have; how adventurous they are; who they can call for advice when a sauce curdles; and so on. In practice neither of the cooks with the different sized cookers is anywhere near the limit of their cooking 'potential'. Any differences in their meals are much more likely to reflect differences in interest, experience and support than they do the addition of another burner or a fan-assisted oven.
I read a lot on Mumsnet that suggests children are often tutored 'beyond their ability' I started an AIBU thread on this the other day to try to explore this further. I think it's an interesting and important area/topic.