I have exactly that scenario atm, and I will admit it is tough.
The rules have changed now.
Instead of pushing children up through the levels as fast as possible, to hit targets etc and show the children are bright, we stay in the same level (so for year 1, the children stay in the year 1 scheme of work).
I absolutely love this. Before, children would be moved up before they were ready, it was like building on sand and as they get older, the work gets harder, but because all the basics aren't secure enough, it all falls apart.
Now we work on mastery, so the children need to master all the elements of the years curriculum.
For instance, whilst his friends are doing 22 + 7, he is doing 'John has 22 pencils and gets 7 more, how many does he have in total?' That no matter how a problem is presented, the child can solve it. He needs to fully understand everything completely. It's great.
You aren't supposed to move up past the year level but in the case of gifted and talented, if you can prove that the level is completely mastered, then the head teacher (or senco or someone) can authorise going to the next level.
In my case, I intend to spend till Christmas proving complete mastery and then move on to year 2 work if I can collect enough evidence and if it turns out to be the right thing for him (its a plan, plans change).
Maybe mrz could add more on it, it is not one of my strengths and I am learning as I go