I think you should not worry.
It is not at all sure that the children currently labelled as G&T WILL be our future scientists, you are getting a bit carried away there.
The interesting thing is that children develop at different rates. Some are G&T as little ones, but then "even out". And more importantly, a lot of children do not do that well at primary. But start to "click" at secondary and end up doing extremely well.
I have one child who is GT, but as far as I can see he is just "ahead for his age", and I am not worried about him. He is not bored at school at all, and he just does the normal school work and then is allowed to join the work for the year above (very small classes, y1 and 2 mixed).
I have another child who is remedial for everything (extra help).
TBH, I think they will both end up doing well, eventually, if maybe not in the same way.
The one who is "behind" is my little scientist, he can concentrate so well, and builds difficult things, draws complex charts and does well in abstract thinking, yet struggles with writing.
To segregate children into G&T and "ordinary" does not do justice to the wide variety of skills and rates of development of children.
It is all very fluid.
The children who are G&T at 5 may well be "ordinary" by 8, or the other way around. I sometimes work with y1 and y2 children, and I LOVE seeing how different they are, they all develop at an individual rate, there is no "average" or "ordinary" really.
FWIW, the only scientist I know (working for NASA) did poorly at school until he was 14.
It is not as black and white as you think.
I think our lovely State school caters very well for the different abilities.
I am sure you will be able to find a good school as well.