To teach third-graders about the cultures of antiquity, implement creative projects concerning particular ancient peoples. For ancient Egypt, teach students about early language and hieroglyphics and ask them to invent their own pictorial language or have them construct their own pyramids and papyrus paper. During a segment on ancient South American tribes, assign students into groups to create giant murals representing Mayans, Aztecs and Incas, and have each group give a short presentation on their assigned tribe. Projects on ancient Greece and Rome might include dressing up in togas and performing a play on mythology, designing cutout figures of famous Greek or Roman statesmen, constructing models of Greco-Roman architecture or researching and preparing ancient Mediterranean food with parental supervision for a class banquet.
While third-graders may not grasp the nuances of checks and balances or the responsibilities of each branch of government, they can understand the basic layout and duties. Divide your class into three groups, assigning each group a branch of government. Ask each branch to research its basic duties, providing informational material for them to read. Have the class create a flow chart or a mural of how each branch works together, then ask each group to act out in very simple terms what their branch would do in a scenario you provide. For example, if you say that a student at recess was injured because of a broken slide, the judiciary group could make a ruling on who was at fault, the legislative group could debate a law to make slides safer and the executive branch could address the "public" about the accident. Students also could use primary documents to research the founding of the United States government, present short biographies of famous presidents or go on a scavenger hunt for government symbols and facts.
Third-graders can learn about the exchange of goods and services by participating in a bake sale, designing a dream vacation on a budget or visiting a farm and a grocery store to learn about the process of distribution and the difference between a good and a service. Students also can benefit from setting up "shops" in class. Allow them to pick a good or a service to provide -- some ideas might be to sell food, make jewelry, draw portraits or clean shoes. Give each student a set amount of fake money, and let the students take "shifts," alternating between being a customer and a shopkeeper.
To teach third-graders about geography, give them projects concerning maps and modern cultures. For example, have students draw detailed maps of their own home, neighborhood and city. Teach them how to draw basic contour maps, then lay out a few objects of different heights on a flat surface and ask them to draw one. Show students how to use a globe and have them make their own using construction paper and grapefruits. Ask students to research their ancestry and give small presentations about the countries of their ancestors.