Here's a quick list to help you get started with sculpture, no matter what age you're working with.
Materials to Sculpt and/or Carve
Natural clay
Mud
Modeling clay
Sculpey
Paper clay
Bread & glue clay
Paper pulp
Soap
Wax (cheap candles)
Aluminum foil
Potatoes, turnips (root vegetables)
Boxes
Straws
Plaster (dried, to carve)
Sculpting Tools
Popsicle sticks
Twigs
Butter knives, forks, spoons (use metal and heat in warm water for wax and soap carving)
Toothpicks
Tips
Add in: sand, glitter, buttons, small plastic toys, etc.
Connect parts of sculptures with toothpicks or straws.