Most students will go into a pre-algebra program after Sixth Grade Math with Confidence.
Kate Snow doesn't have reviews or recommendations for higher levels of math, but click here and scroll down to the comments to see a few programs she likes.
For post-elementary, pre-Algebra math, some of Dr. Bauer's recommendations include (alphabetically) Math Mammoth, Math-U-See, Right Start Mathematics, Saxon Math, and Singapore Math. The one that is best suited for you depends on your student's learning style, strengths, and weaknesses.