Absolutely. I find that I had to add in extra review(just going back and printing off old lessons or using the review websites worksheets that are included) for my kids, but now Math Mammoth offers extra review books. Before the extra review I added my daughter's end of year evaluation scores were okay. After, I added in more review her scores shot up, so much that the evaluator was like, "is that all you're using"? LOL Your kids may not need extra review though.
I used to use Singapore Challenging Word Problems for extra work in that area, but find Math Mammoth word problems to be just as challenging and thought provoking.