Of course, the focus of the lower grades lies in the cultivation of learning interest, the focus of the middle grades lies in guiding the transformation from image thinking to abstract thinking, and the senior grades begin to stimulate the ability of mathematical strategic thinking. At present, I haven't seen any good books on mathematical thinking training in primary schools. I don't know what book to use We all develop our own projects, and the books on the market are of little value, and most of them are deceptive. If you want to study this problem, I suggest you look at the new classification of cognitive goals.