A great resource for composting at school and keeping track of data is Do the Rot Thing. It has a great illustrated detrivore scavenger list that kids could use exploring under rocks and logs outside. Keep the learning going by building a habitat for the classroom:
You will need
1 medium, clear storage box, such as Sterlite
dead leaves from local trees, such as oak and maple
potting soil WITHOUT fertilizer or pesticides
a small log
spray bottle for water
drill plus app. 1/4" bit
Drill holes around upper edge of container or in lid, carefully removing plastic bits and sanding if necessary. Fill bottom of container 1/2" - 1" high with gravel. Lay dead leaves over gravel. Top with soil, leaving 4"-6" open. Add log, more leaves, a few small carrot pieces, and other natural items like acorns or moss. Spray generously with water initially, then check for dryness and spray as needed.
* Organic carrots are best. "Baby" carrots are often larger carrots bleached and tumbled. Bleach is not good for detrivores.
Good classroom detrivore:
Pill bugs (Look for shed skin. They often eat their skin, but you may find what look like fingernail clippings. Mine have had several generations of babies.)
Snails will be happy there, but needs fresh leaves (lettuce, spinach, NOT tree leaves).
Worms, even red wigglers, need more space than this.