We have been dealing with some of this with ds, now 10. He will get a worksheet and it will take forever to complete although his abilities in math are very high. There is a boredom factor, and it is worse as time goes on.
Lately I have been working on info to send to school to have him assessed for gt in math and had to go through pre-algebra up to algebra work very quickly to keep him at all interested. As I said in another thread, I explain a concept and he already knows it or learns it so quickly it is as though he already knew it. The number of problems he wants to work on for that particular idea are in the single digits and then move on (and he does get them right). He is ok if the next set of problems incorporates older concepts, of course, so that is the way that we will have to build in practice on all levels, the easier stuff within the newer stuff.

This is gonna be hard to get them to buy at the school perhaps, because the number of problems he is doing is not huge (they will probably claim he has no passion for the work, for one thing) but his passion has been quashed for 5+ years now so it is going to take some figuring out to get him back into math. He said he would probably be interested in calculus, which I do not doubt, although definitely not yet ready.

I can not advise skipping the repetition, but it is my gut reaction to all this for my ds....however we are still a work in progress over here! Good luck to you and your ds!