Explain to the students what a compost pile is -- biodegradable waste that decomposes into a nutrient-rich soil additive. Buy a small compost bin or build one out of wood scraps and store in a discreet location on the school grounds. Begin composting on Earth Day by having students dispose of compostable material from their lunches into a classroom container. Have a volunteer dump the container into the compost bin at the end of each school day. Continue throughout the school year. Encourage the students to bring in old newspapers or bags of leaves from home to add to the bin. When the compost is complete, donate it to the community garden or create a garden project right on the school grounds for summer school students.
This project is a good way to combine Earth Day ethics with another topic you are studying. If you start an in-class recycling project, chances are you'll end up with lots of bottles, cans and cardboard. Encourage the students to build something with it that fits in with a topic that the class is studying. For example, if you are studying world history, build some pyramids. If you're working on American history, create a mosaic map of colonial America with bottle caps. Make sure the recyclables are cleaned well before beginning.
Turn your fourth graders into a team of volunteers and engage them in a clean-up project. Since Earth Day falls on April 22, the ground may already be covered with trash, leaves, branches, and other detritus after the snow melts. Plan a "Beautification Day" for the school property or via a class trip to a local park. Bring trash bags, gloves and rakes and let your students make the Earth a better-looking place. If you have a compost project at the school, separate the trash from compostable and recyclable materials. Take pictures of the students in action to create a bulletin board back at the classroom.
Contact the managers of your local grocery stores to let them know about your coming project and ask for their involvement. Collect stacks of paper grocery bags from the stores and distribute them to your fourth grade students. Using markers, crayons and paint, have the students decorate the bags with Earth Day-themed designs and slogans such as "Reduce, Reuse, Recycle," "Treat the Earth Well," and "Go Green!" Return the bags to the stores so they can use them. Alert the local media so they can cover the event and provide some PR for both Earth Day and your school.