Sorting and classifying historical knowledge can make knowledge organized and systematic, which is not only convenient for memory, but also can cultivate inductive ability. For example, after "Ancient History of China" is finished, the contents of textbooks can be classified according to centralization, social and economic development, tax system evolution, land system development, scientific and cultural development, ethnic relations, foreign relations, peasant uprising and peasant war.
For another example, the content of China's ancient cultural history can be classified according to the clues of astronomy, medicine, agriculture, scientific and technological works, painting and so on. Classification can play a multiplier role in consolidating knowledge.