I love Singapore Math. Wish I had it as a kid. Our 6 year old started on this for second semester of Kindergarten since she was flying through her K curriculum. I like the different workbook activities which make it more exciting than doing the same "problems" over and over. The textbook introduces it well. I also recommend the teacher's book...the original one by Singapore Math (not others that just give answers and "lesson plans" that really just say which assignment to do for the day...NOT helpful like the Singapore one). Gives LOTS of activity ideas that help to grasp the concepts.
I started my 2nd grader on 1B. She did fine and now she's on 2A. I think it's great! She seems to like it. She's never complained, but it's challenging at times. I just wanted to point out, in case some of you may not know, the levels aren't the same as grade levels. It's important to test to see what level they should start at. My DD's curriculum suggested she start at level 1B, as long as she scored high enough, and she did, so that's where we started.
I love Singapore Math because it's so easy to use. There are no complicated concepts to teach... just straight forward math the way I was taught as a child. We have only been using it for four months, and both my children (ages 6 and 8) have learned so much! And they beg to do math before any other subjects!
I have a kindergartener who was moving very quickly through math. He is a 6 year old kinder, so I purchased 1A and 1B. He loved math everday and grasped concepts quickly. By the middle of 1B we hit a snag. Singapore math is advanced, so I felt were were working on a 2nd grade level and he just wasn't ready. Not knowing how to continue using Singapore math with him, we took a break and use it sparingly (he is after all, a kindergartener). But I would like to find another curriculum for him next year.
My 3rd grader moved though 2A, 2B and started 3A this year. The mental math component is awesome and he and I are both doing mental math more quickly. He is a hesitant math learner and said he likes Singapore math better than what he did in PS. We'll see how he does on his test scores in 3 weeks.