We are using this math curriculum right now and I love it. It begins with the absolute. Basics but goes through all of it so thoroughly. It makes me confident in teaching and knowing my kids are really understanding and getting a very good foundation set. They love their work books, the pictures are large and fun for them to work on.
My first grader used Singapore Math's EarlyBird books in her Kindergarten years and enjoyed the books. I also found it easy to teach her Math using these books so when she entered first grade I wanted to continue with this curriculum. The Primary Math 1A workbook is challenging enough so she doesn't get bored but still at a level that she can do on her own with minimal supervision/teaching from me. This is an excellent Math curriculum and we will continue using it for as long as we homeschool.
I use Singapore for my 4th grade son and my first grade daughter. My daughter just finished the KA and KB Earlybird books and they really gave her confidence. They move very slowly so it builds confidence. We started 1A which I believe moves very quickly and if your child is not confident may overwhelm them a little. We are using the Math-u-see blocks with it and it has made it much simpler. She is flying through it with confidence so far.