Many Math professors, who have looked at the Singapore K-6 Math Books, are strong advocates of them because these books
1. Do an especially good job in training students in Basic Skills and
2. Do an especially good job in providing students with Conceptual Understanding and
3. Provide an especially good background in Arithmetic and Arithmetic word problems, for the learning of Algebraic calculations and for learning how to solve Algebraic word problems.
4. Do an especially good job in training students in non-trivial Arithmetic word problems; while American texts largely avoid non-trivial Arithmetic word problems.