This End-of-the-Year project idea came from The Owl Teacher and her emails. I just modified it slightly and offered it back to my own TPT network. It is a GREAT idea and I hate to see it only used for elementary students.
You will need a penny for every pair of students in your classroom. Be prepared for the causes and effects they come up with as they try to "out stump" their partner in this End-of-the-Year review.
As a NEW teacher I would never try this but as a 20+ year veteran teacher, my students have always like to TRY and stump me. They have not yet, but you just never know what cause they may remember.