The ancients had three explanations for "teaching without class": first, teaching without class; The second is to teach not to choose people; The third is to let the public accept talents. The first two meanings are the noumenon of "teaching without class" and the basic principle of education; The latter meaning is the application of "teaching without distinction" and the popularization and application of educational principles. Although Confucius said "education has no class", equality is the first meaning of "education has no class". "Teaching without distinction" highlights the value concept of "everyone is equal before education". According to Confucius, people, rich or poor, should have equal rights to enjoy education. Of course, Confucius' indiscriminate teaching excludes women, which is the limitation of his thought. However, Confucius advocated and practiced a typical civilian education, which was not only the progress of the education system, but also the progress of social concepts compared with the aristocratic education implemented in his previous era. Justice is the second essence of "teaching without class". Justice is a moral sentiment based on equality and higher than equality, and it is a great discovery unique to human society. Xunzi, an ancient thinker in China, believes that justice is an acquired quality, that is, "no knowledge, no justice." Change is the third essence of "teaching without class". The so-called change of ideas here means that only through education can a person's personality be changed, thus changing a person's destiny.