Who will pay for sending a banner to the teacher after graduating from a large class?

After graduating from the big class, parents paid money to send banners to the teachers. Because the children who graduated from large classes are still young, the cost of sending banners to teachers still needs parents' money. The child has no financial ability and sincerely sends a banner to the teacher. The production cost of a banner is only a few tens of dollars, which is not a financial burden for parents and does not violate teachers' morality. Therefore, after graduating from a large class, parents paid money to send banners to the teachers.