Kumon is boring but there is a role for it, I think. We just bought their books online, which is very cheap. At some point, your child has to get down cold math facts for addition, subtraction, and multiplication to really excel in math.
We did some Singapore Math for awhile plus Kumon sheets. For my 4th grader, I moved to workbooks from Brighter Child. They have very nice, simple workbooks about Algebra and Geometry, which are really good.