Domestic textbooks are all abstract concepts of addition, subtraction, multiplication and division taught in the fourth grade, some in the last semester of the fourth grade and some in the next semester of the fourth grade. This is in line with the law, the law of knowledge itself, and the cognitive law of children, so it is also in line with the law of teaching. I published an article in Zhihu entitled "Teaching Secrets: the Best Coupling of the Three Laws". The key is to make knowledge, cognition and teaching in the best coupling state, so as to obtain the best teaching effect.
Unfortunately, there are too many illegal things at present! Some institutions actually teach preschool children to learn three-digit multiplication. Tossing children and parents, of course, some parents like to be tossed like this. This is the market. Blindly ahead, can children understand? The answer is: yes, but the price is too high. This is at the expense of children's childhood happiness and happy childhood, and also at the expense of children's all-round development, replacing all-round development with abnormal development.
In the whole primary school stage, children have two weaknesses: abstract thinking ability and spatial imagination ability. The solution, I sum up as a general formula: turn intangible into tangible, and then lead to intangible step by step; Turn abstraction into concrete, and then lead to abstraction step by step. Specific to the topic mentioned by the subject, different teachers may have their own different solutions, and truly: everyone knows the second day of junior high school, and everyone will know it. In this case, I will go around a big circle and treat both the symptoms and the root causes.