Math Rocks is supposed to be a more problem solving approach. It is great, but the issue is that you'll not see anything coming home. This can be frustrating. Most Math Rocks kids have enrichment outside of school. My son does not attend any other classes outside and I have to make sure there are no gaps.
I worry that this might be a bigger concern in middle school.
Plus - based on my guess, the problems can be of AMC / Math Olympiad nature. Am not sure how well our teachers can handle it. My son got into the program in 4th and it is really hard for me to assess how much this program has helped him. I do trust that the content is great and probably one of its kind in the nation - but I have little faith in how it is delivered or drilled.