The idea came from book Earth Child, one of my favorite homeschool science books for 2nd grade.
We filled a jar with dirt, horse manure, partially composted leaves, a few food scraps and some worms. We covered the jar with a dark pillow case. Martina watered it often and we watched it for a week. Bean sprouts grew. The worms moved around a bit. We saw a few trails inside the jar.
Today she turned the worms loose in some tilled up soil. The contents of jar smelled bad enough to make her pale. Vermiculture is not our speciality!