One point to note is that a child that appears to be G&T at the age of 2, 3, 4 (in fact any age really) can be overtaken at any point by their peers.
I do know that there was a DC in my sons class who appeared very bright compared to the rest of the children in the class (best at reading, writing, maths and sports) and certainly his mum had numerous discussions with the school regarding their DCs educational provision. My DC didn't appear to be anything more than a middle/good performer and I accepted that.
The class did their yr 2 SATs and the majority of the children gained level 3 (the school did not test/rank higher than this).
At the start of yr 3 all children were assessed during the first week. A very small number were given further assessments the following week. My son was one of those who did the additional assessments. The parents, as far as I can tell, accepted that this was standard practice at the school and left it at that.
Later in the year came the parents consultations. I was informed that my DC had been assessed at level 4b for maths and 4c for English at the start of the academic year and had been placed on the G&T register.
Interestingly the mother of the DC who had appeared quite advanced in yr 1 said that she was a bit annoyed with the school as she felt they had lead her to believe that her son was much brighter than he now appeared to be. She felt they had "talked him up" too much. I felt this was interesting as the school had never suggested to me that my DC was anything more than average/good in performance.
SATs assessments are done every year at my DCs school and the G&T register changed accordingly.
My DC was assessed as level 5 for maths and level 4a for english in January (yr 4). However, I am not kidding myself for one minute that his performance will not plateau out at any time and other children may overtake him academically.
I have never felt the need to approach the school to discuss his provision. I do know that he does extra literacy this year and last year did advanced maths. My DC thoroughly enjoys going to school and is very happy there. I think this contributes greatly to his academic performance as he sees the learning process as enjoyable rather than a chore.
I appreciate that not all schools are as effective in nurturing the academic potential of children but it is important to allow they time to do this before stepping in.