To see how caste worked in ancient India, try dividing your class into castes. Take a box or a jar and put inside it four pieces of paper that say "Dalit", two pieces that say "Brahmin", four pieces that say, "Slave", three pieces that say "Vaishra", and two pieces that say "Kshatriya". That's 15 pieces; put in one piece that says "Shudra" for each of the remaining kids in the class. Shake it up to mix the pieces.
Without looking, each kid can draw one piece of paper. Then each caste can get together (the Shudras will need to form more than one group) to discuss what their concerns and issues are. Each caste should pick one goal - getting more land? getting out of debt? being richer? having better food? - and explain how they would convince or force the other castes to help them with their goal.
Will the castes cooperate and compromise, or try to force each other to do things? What methods are available to each caste?
To find out more about people in ancient India, check out these books from Amazon or from your local library: