On May 30th , a "demand determines the value” activity was held in Zhonghai campus. The Children's Day celebration of grade five was ordinary that students took their unused items to the school and exchanged with other students. How to judge the value of second-hand goods? How to let the article to obtain higher prices? How to make more and more people like and demand their goods? These require students to explore and practise. Today, the classroom changed into a market, supermarkets or canteens. Students resorted to use all their skills to attract business, such as: lottery draw, largess, discounts, auction and so on . This is not only a market, a fair ,but also a learning path , a hymn of life!