"A gentleman knows what to teach, what to teach and what to waste before he can be a teacher" means that teachers can only be competent for their work if they understand the factors of educational success and the reasons of educational failure. It shows that teachers need to master the knowledge of pedagogy, psychology, textbooks and teaching methods, that is, educational theory knowledge.
Source: The Book of Rites: "A gentleman knows both the principles of teaching and the principles of teaching, and then he can be a teacher. Therefore, the teaching of a gentleman is figurative. Tao and Fu La are strong, restrained and open-minded. "
Translation:
A gentleman can become a good teacher if he knows both the experience of successful teaching and the reasons of teaching failure. Therefore, teachers teach people, that is, to inspire and induce: to induce students without pulling; Persuade but not suppress; Instruct students to study, not tell them the answers directly.
Extended data:
Xueji is an ancient educational paper in China, one of the monographs on ancient laws and regulations in China (The Book of Rites of Little Wearing), and the earliest educational and teaching monograph in China and even in the world.
Creative background:
The Book of Learning is one of the Book of Rites, which was written from the 4th century BC to the 3rd century BC. According to Guo Moruo's textual research, its author may be Ke, a student of Mencius.
Gu Shusen supported Guo Moruo's view that Xue Ji was written by Le Zhengzi, a Confucian scholar, at the end of the Warring States Period, and borrowed ideas from the school, probably by Ke, a disciple of Mencius. Gao Shiliang also agrees with this view, thinking that Xueji is a work of the Warring States period, and the specific time is in the late Warring States period.