Project WILD – one of the most-used sets of environmental education curricula in the US. grades K-8 with some flexibility in the grade levels. You can’t buy the materials – it’s given to you when you attend in one-day (or more) workshop. You get the books while the actual materials are simple and cheap.
Don’s hint – get a plastic bin for each activity you will use and keep it pre-loaded with all of the things, be they paper towels, paper clips, whatever. Add a few empty trash bags and a photocopy of the exercise and the teacher’s hints. Then you can just grab and run.
A lot of learning about conservation, environmental and ecological principles can be taught through games and activities. Project WILD and its companion, Project WET serve to provide the teacher with dozens of such activities that have been teacher-written, then teacher-tested, and revised so that they just simply work. Most are keyed to objectives. Read more at http://www.projectwild.org/
One more thing – here a free sample lesson. It’s for young children, and it’s about how fish use their bodies when they swim. http://www.projectwild.org/GrowingUpWILD.htm and click on the “Sample Activity”.