"Duck stuffing" means that duck farmers put columnar feed with high sugar content into the duck's mouth to fatten it quickly. Here is a metaphor for indoctrination education.

Indoctrination education, also commonly known as "injection education", is characterized by emphasizing that educators instill knowledge into students. Indoctrination education is the product of the development of human society to a certain period. Its formation and development are closely related to people's different understanding of knowledge, children and teaching under certain social conditions.