I do a lesson with my first graders, but 4th graders would love it too. I I got it from here I think....Create an Ant Playground (who gave us this lesson?) I read them Two Bad Ants by Chris van Allsburg (pardon my spelling) and we talk about paper sculpture techniques. I cut mat board into 6 inch squares for the base. It is really a lesson in size relationship (big and small). For the little ones, the book, In the Tall Tall Grass actually works better at visually describing size relationship. The first graders love it, 4th graders could really take it pretty far. I also do paper sculpture masks with first graders and hanging paper sculputres. All of which could be done at a more advanced level with 4th grade.