Try to achieve a sense of interconnectedness and symbiosis among these organisms. Some plants are parasitic on others. Vines can intertwine through the whole thing. Cloth, sand, soil, etc. Special lighting in different colors can be used to simulate sunlight filtering through the trees.
Sound effects can enhance the mood further.
Make announcements to other classes and teachers about the project and its significance. In the weeks following the initial installation, the teacher and small groups of students disassemble the installation gradually. This is to symbolize the disappearance of the rainforest.