it's hard to just say "try this" when you dont have more info.
I'd get a good scope and sequence to find out what to learn when. Try worldbook.com under the parent's section or the "What your X-Grader SHould KNow" series by E.D. Hirsch.
Then, figure out his learning style, your teaching style, how much time you want to put into planning, how often you want to use the library, your budget, how autonomous he is, how much reading/writing he can handle, your religious preference, your local laws...and go from there.
Personally I love Saxon math for one kid and Singapore for the other. Math is the only thing I use prepared curriculum for.
meg