I used some workbooks from the critical thinking company last summer (math analogies and "building thinking skills"). The math analogies book was great, I liked the variety of problems. Building thinking skills was ok, sort of hit or miss. I also have the primary grade challenge math book, he worked through a couple of lessons last summer but did not finish it.
I'm torn between giving him problem solving type of work and a regular curriculum like Singapore math. I don't want him getting too far ahead and being even more bored in math at school. They don't offer any math acceleration in the district except in the highly gifted program, which I doubt he will qualify for (they test for that next year, and this year's cogat score put him at the moderately gifted level). At the same time, he is totally ready for more advanced math, and I think he will be likely be bored anyway next near.
