I bought the sixth-grade Teaching Textbooks for use in our homeschool. It's a lot of fun! I would recommend getting the grade HIGHER than what you're starting now if you'd like to try it out (better yet, peruse the website, look at the tables of contents, allow your child to take a practice test and draw your own conclusions as to what is best for your child!). It says sixth grade on the cover, but I wouldn't get too excited about that part as much of the first quarter appears to be review. Place value and long division are re-covered in these first lessons. We have begun Singapore Math for our fifth grade studies, but I am using these Teaching Textbooks for our lesson about once a week. It slows us down a little bit, but I also figure that it's fun and it can't hurt to review on a weekly basis, or go over previously learned material in a new and different way.
I'd highly recommend getting this set, but I will warn you that it's a bit difficult to install. I finally had to resort to calling the company on my cell phone while I was at the computer doing this process. Hopefully, this review was helpful to someone thinking about purchasing math curriculum for a child. Teaching Textbooks are available through CBD as well as the company's own website for the *same* price, and shipping is included. I would advise against getting an extra workbook in the lower grades, however, as the answers to workbook pages are easily worked out on a scrap paper.