A key thing to realize is that the Common Core is a set of standards rather than a curriculum. If you want to see how they are presented:
http://www.corestandards.org/Math/So the material they've bought into is one company's attempt to cover the standards with a curriculum. But still at the bare minimum, the easy free path is subject acceleration by giving him progressively more advanced material within the current curriculum. That could be within class or having him attend a higher level math class (one question being whether he his a self-learner or needs instruction.)
If you are looking for parallel enriched work, then have a look at The Art of Problem Solving as they have material that gets deeper into problem solving and thinking. Other people talk positively about Singapore Math, which I'm not familiar with.
