There is nothing inherently wrong with the principle of breaking 21 down into 20 + 1. But if a student has already learned how to solve problems directly, and the teacher insists on forcing the student to break the number down into its component parts anyway, that is just "teaching the new material without changing the old pedagogy."
他舉例說，把二十一拆解成二個十加一的想法原本沒有錯，但如果有學生早就學會直式加減，老師仍然一成不變地要他們繼續拆解數字，等於還是用「舊模式來教新教材」。