I love Singapore Math and I think it's an excellent math program. It's tricky to find out if your child should use the K or 1st grade program. As far as I know there is no placement test into 1st grade. If your child passes the 1A test then it means that he is ready for 1B.
You may need to look at the sample pages and see what would be the best fit for your child. You may want to start with 1st grade or the second half of the K. You will see. The material is cheap so if you don't find a perfect match it's not such a big deal.
