Louise and Stella were friends. One day at school, the teacher was a bit late for her class. So Louise and Stella began making paper aeroplanes. “Let’s see whose plane flies higher,” Stella said. Soon, the other girls in the class joined in the fun. Suddenly, their teacher walked in and everybody fell silent. “You are making so much noise! And what was it all about? Wasting paper?” Then she picked up a paper aeroplane that lay on the floor and said, “If this continues, soon there will be no trees on Earth. All the birds and the animals will be homeless, and they too shall perish.” Stella could not understand. “Why teacher?” she asked, meekly. The teacher said, “Paper is made from trees. If you waste it, more trees will be cut to manufacture more paper.” Louise, Stella and all the other girls pledged not to waste paper again.