Plastic pots store seeds. Old newspapers make paper containers. Even nature recycles. When plants and animals die, they fertilize the soil or, after many centuries, become coal and oil. In many countries, recycling is done routinely.
New paper is made from old ones.
If you recycle one ton of paper, you can save 17 trees. Cans are crushed and melted to make steel for cars. If there are recycling centers nearby, collect used items and take them there. You can even organize your class to do so.