This is interesting, esp. as schools are cutting down recess/playtime/phys ed to nothing, and the nutritional value of the food kids eat in schools is completely inadequate. Brains can't work well if the rest of the body isn't being taken care of.
Bottle Ecosystem, This is the most awesome class idea to teach ecosystems! Its self contained and you can observe the activity for the rest of the year. No mess no fuss and all of this cost about 17 dollars.