Going to college and then volunteering in high school is a way for college students to return to their alma mater to promote high school practice. Many college students spontaneously organize together, and high school graduates return to their alma mater to give lectures on university obligations. So ask college students to go back to their alma mater's high school to promote their own practices. This behavior can encourage their younger brothers and sisters to study hard and actively prepare for the upcoming college entrance examination. It belongs to a kind of voluntary service.