Go to your local fishing store and buy real live worms (or dig some up). You can then build a worm habitat in an aquarium in your classroom. Kids love to feel, touch, smell the worms. Caution: Watch kids closely as some will attempt to eat the worms.
In sensory table add potting soil and gummy worms with small shovels and hoes. Everything Preschool >> Themes  >> Worms >> Science