After returning to the State of Lu from Qi, Confucius had originally placed his hope for realizing his political ideals on the ruling class of Lu. However, the political situation in Lu had further deteriorated: the authority that had already shifted from the ruler to the high ministers was now descending even further, to the point where "retainers (family stewards of the great houses) were controlling the state's commands." Confucius had previously believed that when "rites and military expeditions emanated from the high ministers," the crisis of "the world being without the Way (Dao)" had already begun; now, the situation was even worse than before. Assessing the circumstances, he pointed out that ever since retainers began manipulating state orders, it was rare for them to hold power for more than three generations without losing it, and he asserted that the rule of retainers would not last long. Amidst this chaotic political landscape, Confucius naturally did not wish to collude with the powerful ministers and therefore refused to take office. During this period, he concentrated his efforts on studying the Classic of Poetry (Shijing), Book of Documents (Shangshu), Book of Rites (Liji), and Book of Music (Yuejing), and devoted himself to education.
In his private school, Confucius engaged in teaching, with students coming from afar not only from the states of Qi and Lu within present-day Shandong Province but also from Chu (Hubei), Jin (Shanxi), Qin (Shaanxi), Chen (Henan), and Wu (Jiangsu), drawn by his reputation, covering nearly all the major feudal states of the time. Confucius adhered to the educational policy of "teaching without discrimination" (you jiao wu lei), accepting anyone who could be taught, as long as they "offered a bundle of dried meat as a token of respect," and he would educate them. He recruited students inclusively, without restrictions on social status, wealth, age, or nationality, and this unconventional method of accepting disciples attracted widespread attention from the entire society, including both upper-class nobles and commoners. Many young people became his students during this period, such as Yan Hui (thirty years younger than Confucius), Zi Gong (thirty-one years younger), Ran Qiu (twenty-nine years younger), and Zhonggong (twenty-nine years younger). In response to this situation, Nanguo Huizi once asked doubtfully, "How mixed is the company at the Master's gate?" Zi Gong (a wealthy merchant and eloquent disciple) replied, "The Junzi (Exemplary Person) rectifies his conduct to await all who come from the four directions, and must never turn anyone away, just as a good physician's door is crowded with patients."
Confucius said, "By nature, people are similar; through practice, they become far apart." He believed that everyone could be improved and elevated through education. Among his students, some had good natural qualities while others had poorer ones. Yet through his teaching according to their aptitude, tireless instruction, and skillful guidance, many became renowned virtuous talents and scholars. He advocated that learning should be practical and down-to-earth. He said to Zi Lu (a brave and impulsive disciple), "You! Shall I teach you what knowledge is? To know when you know, and to admit when you do not know—that is true knowledge." Only what you know can you say you know; what you do not know, you can only say you do not know—this is the truly wise seeker of knowledge. Confucius established private schools not only to cultivate scholars but also for the purpose that "those who excel in learning should serve as officials." Through this kind of education, he aimed to train and produce outstanding talents capable of ordering the family, governing the state, and bringing peace to the world, enabling them to participate in politics and thus change the chaotic state where the Dao (Way) was not followed, hoping to realize an ideal society where "the elderly are comforted," "friends are trustworthy," and "the young are cherished." He was not merely teaching books but teaching people. He taught people to become Junzi (Exemplary Persons), first requiring noble moral character combined with mastery of the Six Arts (rites, music, archery, charioteering, calligraphy, mathematics)—that is, possessing both virtue and talent. Second, one must be open and magnanimous ("The Junzi is broad-minded and at ease"), practice what one preaches, act before speaking, be fair to people and affairs, and show no partiality. In answering Zi Lu's question about the Junzi, he said, "Cultivate yourself with reverence to bring comfort to those around you (relatives and neighbors), and to bring comfort to all the people of the nation."