As I previously said, I am not a fan of teaching soil! My classroom is always covered in mud and dirt from the experiments (ick!). In the past we created soil tubes to demonstrate the layers of soil. However, it was always really hard to get the dirt in tubes, and the soil layers would sink quickly. Third-graders are not too impressed when their topsoil ends up being bedrock within 15 minutes.
This year, I wanted to demonstrate the layers of soil in a different way. I chose to make edible soil! They LOVED this. A few weeks before I needed materials, I sent out a Google Doc to parents to sign up for different parts of the "experiment." For a class of 27 kids, I needed one box of Cheerios, one box of Cocoa Krispies, two bags marshmallows, three bags of gummi worms, cups, and mini M&M's. First put in Cheerios, then marshmallows, then Cocoa Krispies, sprinkle in some M&M's to be humus mixed in with the topsoil, and finally place a scary gummi worm on top :-)
Cocoa Krispies: Topsoil
Mini M&M's: Humus
Gummi worms: creepy, crawly worms
I called kids up in groups of three to create their treat and label it. Once everyone had been served, they could eat it as a yummy snack. Try it, your kids will love it and it's a nice, memorable experiment for them :-)