Third grade. According to the Chinese vocabulary in primary school textbooks, we can know that the new word "Mo" in lesson 16 of the second volume of Chinese in grade three is a compulsory vocabulary for primary school students. A primary school is a school where people receive primary formal education. It is an important part of basic education and belongs to the category of nine-year compulsory education. With the development of society, kindergartens have opened in front of it. 3-6 years old are kindergarten-age children, and 6- 12 years old are primary school-age children. At present, the length of primary education is 6 years. The primary education stage is followed by the secondary education stage, that is, from primary school to junior high school.