Enlist the students to help you make the materials for your fort. Ask families to donate clean, light-colored sheets. Spread the sheets out on the floor and let children decorate them. They can use markers to draw on designs, or you can let children fingerpaint on the sheets. Give children writing practice by encouraging them to write their names or the alphabet on the sheets. When the paint is dry, staple or sew the edges of the sheets together to make one large canopy.
Make your fort into an indoor campground by pretending it's a tent or log cabin. Spread out sleeping bags or blankets on the floor inside. Create a pretend campfire just outside your fort. Paint rocks black to look like charcoal and set them inside a bowl. Cut flame shapes out of red and yellow paper and prop them up in the rocks. Turn off the classroom lights, then tell stories and let children shine flashlights on the ceiling of the fort.
Encourage children to be explorers by pretending the fort is an undiscovered cave. Once the fort is up, fill it with 'secret' objects that children can discover. For instance, make fossils by pressing plastic objects or rocks into clay. When the clay dries, scatter the fossils throughout the fort. You can also place treasure maps in the fort, then hide treats or toys somewhere nearby for children to find. Place newspapers and paper bags inside the fort so children can design their own explorer hats.
If the weather is nice enough, take your fort materials outside to set up. Hang sheets over low tree branches or use them to cover a fenced-in play yard. If you're setting up on top of dirt, bring a tarp or towels to spread on the ground. Children can run around outside and play, then return to the fort for water or to relax in the shade. Keep coloring sheets and books inside the fort for children who want to stay inside.