It is a very important link to stand up in class and say hello to each other between teachers and students. First of all, it is a symbol of etiquette. Students respect teachers, and teachers respect students. Secondly, it can quickly let both students and teachers enter the classroom.

Before class, students often haven't calmed down from the ten-minute break. Standing up is the watershed between recess and class, and it is also the node of subject alternation.