My DS1 is on level 5 at the end of Y5, not Y6. I wouldn't call level 5 at the end of Y6 'gifted' tbh. Just on the higher side of average... In my DS1's class of 31, at least 17 are expected to get level 5 at the end of Y6, and 4 of those are expected to get level 6 in the SATS.
And if you have no money (like me) and weren't preparing your DC for the 11+ from Y4, then you missed a trick, IMO.
I wouldn't for a moment assume that my DS1 would get to go to a private school where I can afford none of the fees. So I have been prepping him myself for the 11+ since the start of Y4. He sits the test in September, and is currently doing about an hour to an hour and a half each day. Through CHOICE. Mostly working on his weakest area, which is his comprehension, he is only a 5b in that currently.
His Maths we aren't worried about, he is teacher assessed as working on level 6 work, but when the G&T group go to the Secondary, he easily manages L7 work, and touches on L8. At the end of Y5, not Y6.
Why do you feel that you should get for free what others have to pay for?