June 5 th is World Environment Day. This makes us pay more attention to our environment . When Wang Boxuan, a Beijing high schoolboy , uses up his exercise-books , he does not throw them away . Each one is kept at his school, together with hundreds of exercise-books that are given by other students . Then they are sold to a paper making factory in Beijing . The paper is recycled and used again by students and teachers in the school . At the same time , the money that is made from the sales goes to poor areas . People there use the money to plant more trees and grass . Sandstorms( 沙尘暴 ) from this place often do harm to Beijing in spring . Wang's school is one of the schools in the capital that take part in the "Green Promise" environmental protection activity . So far , nearly 80% of the students have joined in the activity and collected more than 87 tons of waste paper .