The Once-ler uses the Truffula Trees to knit Thneeds. Few first-graders have the manual dexterity to knit sweaters in class, but a basic crochet lesson can give them an idea of how natural materials can be used to create clothes. If possible, bring in some carded wool and a drop spindle and show them how sheep's wool can be turned into yarn. Give each child a plastic crochet hook and instruct them on how to crochet a basic chain by first tying a knotted loop, then pulling a loop through it, and continuing on. Some kids may work best with fingers instead of the crochet hook. If you have parent volunteers available, get some help so that kids can be worked with individually and not get frustrated.
The Once-ler tells his story to a young man who comes to learn about the Lorax. A hermit locked in his tower, the Once-ler communicates through his Whisper-ma-Phone. Craft tin can telephones for the kids so they can talk-whisper to each other in the same way. Carefully punch and sand smooth holes in the bottom of two clean tin cans and string nylon string through both. Knot the ends so that when the cans are pulled apart the knots keep the string stretched between them. Have the kids talk quietly through the cans and hear the sounds travel through the vibration of the strings.
The Once-ler lowers a bucket from a pulley at the top of his tower so that the young man can pay him for his tale. Thread kite string over a wooden spool hung from a wire hanger hooked near the ceiling of the classroom and use the pulley to draw up plastic sand pails or similar small containers.
When the Once-ler begins to make Thneeds, which are useless, the Lorax insists "no one on Earth" would buy one. He's immediately proven wrong when a "chap" comes along and and pays up. "You never can tell what some people will buy," the Once-ler tells the Lorax.
None of the destruction in the book would take place if foolish people were not buying the useless product the Once-ler was making out of the resources there. Brainstorm with the kids some good and bad reasons to purchase products. Show photos or video of some examples of products with little use but wide popular appeal. Bring in magazines and have the kids make collages of products from the advertisements that are good and bad values.
The Once-ler's activities pollute the air and water. Show how common household runoff can have a huge impact on a river or lake system with a simple experiment with soap, oil and water.
Many water birds and sea animals use a coat of oil to protect their fur or feathers from becoming saturated and allow them to live on or in the water. Mix olive oil and food colored water in a clear bowl or bottle and explain as it separates that oil and water molecules separate naturally. Add a little powdered detergent to the bottle and show the kids how if detergent pollutes a water system, the oily coating on animals can no longer protect them from water saturation.
The last hope the Once-ler has for the return of the Lorax is if the young visitor begins to rebuild the forest with the last Truffula Tree seed. Grow seedlings in individual cups using a little potting soil and a sunny window. If you'd like the kids to see the process more clearly, plant the seed between a wet paper towel and the side of a clear plastic cup so the root development is visible. Consider buying fast-growing seeds from a biological supply company for faster and less uncertain results.