We've dabbled in Kumon workbooks. They are really great for giving your child confidence and repetition in doing math facts. Alot of kids where we live go to the Kumon Center for hours each week and just drill, baby, drill! on their math facts.
That would be just way too boring for us. The weakness, I think, for Kumon is that it lacks creativity and supporting problem solving skills. It also doesn't really teach you the topic- it sort of assumes that you already know the skill. Singapore Math also doesn't teach new topics that well but was pretty good for problem solving skills.
Singapore Math is in my opinion great at teaching new topics, if used correctly. There is a line of "Singapore Math" workbooks that's not actually part of the Singapore Math system, however; those may be similar to Kumon for skills practice. We have tended to shy away from Kumon workbooks because of the drill aspect. Kumon math workbooks are not in my opinion very good for gifted kids because they're kind of dull. I do believe we bought DS6 a maze one a long time ago, though, and I think he didn't dislike it though it wasn't challenging.
ETA: Here's a sample of the "Singapore Math" workbooks that are not actually part of the Singapore Math system at all-- these of course would not be a proper resource for teaching new concepts:
http://www.amazon.com/Math-Practice...ref=sr_1_6?ie=UTF8&qid=1338251023&sr=8-6(jack'smom, based on what you've written before about using blue and white workbooks, I'm thinking these are what you've used. Is that right? If so, I don't think you can draw any useful conclusions about the Singapore Math program from your use of out-of-program workbooks. It's not that they're bad-- I have never personally used them and wouldn't argue about that, and I'm guessing that they can be used just fine for some skills practice-- but rather that they don't contain the teaching part of Singapore Math.)
The actual Singapore Math system includes teacher's guides, home instructor's guides, textbooks, workbooks, and challenging/intensive practice problems. It is structured to teach concepts using a progression from concrete to pictorial to abstract-- but the key is to actually use the teaching materials instead of just doing workbooks. It's a leading math curriculum for the primary grades, and for good reasons.
Here are samples of some actual materials from the Singapore Math curriculum:
Home Instructor's Guide textbook workbook Challenging Word Problems I'm not shilling for anyone, but that particular site also has the best pricing I've found, especially if you take advantage of a free-shipping deal.
