Thanks for the ideas so far. I've not tried fish oils or the other things. I'm looking for something possibly more psychological/ behavioural with proven effectiveness. I suspect it's partly developmental, yet when i watch his peers and his non-identical twin bro. focusing, it's as if he has this massive disadvantage going on.
He CAN concentrate - eg in one-to-one tuition, in one-to-one activities where an adult completely concentrates on him. But this is not what real life provides.
He is in ana academically selective school and various IQ etc tests indicate he should be in the top quarter but his functioning is in the bottom quarter a lot of the time.
It's not so much my feelings about this but his own that cause me concern, as he calls himself "stupid/ hopeless/ a failure" when he's probably the cleverest in the whole extended family and should be beating his twin at least in anything mathematical.
He was like this as a toddler too - inquisitve and into everything and v actice but wouldn't/couldn't sit and play for any length of time.
His peers for eg will spend an hr or so completely on their own making meccano/ lego models or reading for pleasure or doing sudoku. He, on the other hand, is flitting from one thing to the next. He'll spend longer on something he's interested in, eg trying to make 'inventions' from pieces of string and metal, trying to teach himself to skateboard - but even then, it's a v limited amount of time.
Of course I self-blame all the time....he's rarely ever had one-to-one attention at home for any lenght of time, as I'm a single mum from the start with no family/ outside help. So he's always had to share my attention, whereas many of his peers were the first child in the family of two parents, 4 grandparents, maybe a nanny as well and a mum who didn't work. So I wonder if he's the sort of child who might have benefited from loads of adult input just for him.
Instead, he's had to share just me and his twin has slight Asperger's (hence his completely different ability to concentrate for hours on his absorbed interests alone).
I'm trying to teach him how to fine down his mind and use loads of analogies for him like, "imagine you're like a horse with blinkers on....a blow-torch with a tiny hot flame....an archer fouced just on the target...."
But I think he's too young to 'get' this and translate it into anything useful.
So if anyone else knows of specific strategies that have been shown to help children like he is or a book with specific strategies in it, please let me know.