Before Confucius, "learning is an official", only the children of nobles had the right to education. Therefore, only aristocratic children are qualified to be officials. However, in the era of Confucius, social politics, economy, culture and education were all moving down, which provided opportunities for private schools. Confucius seized this opportunity and started his career of establishing private schools, hoping to train "talents" and officials through education and realize his political thoughts. On the object of education, Confucius clearly put forward the idea of "teaching without class" [7]. The original intention of "teaching without distinction" is that foreigners, regardless of nobles and civilians and national boundaries, can enter school and be taught as long as they have the heart to study. Confucius' disciples came from Shandong, Qi, Jin, Song, Chen, Cai, Qin, Chu and other different countries, which not only broke the national boundaries at that time, but also broke the distinction between Yi and Xia at that time. Confucius absorbed Chu people, Gong Sunlong and Qin Shang who were regarded as "barbarian countries" by Central Plains people, and wanted to live and teach in "Jiuyi", which illustrated the latter point. Some of Confucius' disciples came from the noble class, such as Jingshu, Sima Niu and Meng, but most of them came from civilian families, such as Yan Hui, Zeng Shen, Min Ziqian, Zhong Gong, Luz, Gongye Chang and Zi Gong. And civilian education can better reflect the spiritual essence of Confucius' "teaching without class".

The theoretical basis of Confucius' thought of "teaching without class" is his theory of human nature that "human nature is similar, but learning is far away" [8]. "Sexual similarity" shows that everyone has the possibility of success and virtue, and "learning from each other" shows the importance of implementing education. It is based on the understanding that "everyone can become a virtuous person through education" that Confucius made the decision of "teaching without distinction".

The implementation of the idea of "teaching without class" has expanded the social foundation of education and the source of talents, and undoubtedly played a positive role in improving the quality of all members of society. Therefore, Confucius' thought of "teaching without class" has epoch-making significance in the history of educational development.