The girls and I have been studying the Constitution and the Bill of Rights. I found a great book in the library by Cathy Travis, "Constitution Translated for Kids". It has the wording of the actual Constitution in one column and the translated version right next to the actual wording. It's been great for reading and deciphering the meaning of the Constitution and the Amendments giving me a new appreciation for our governing document.
The back of the book lists some proposed amendments for the students to consider with points for and against a proposed amendment that the students can debate. It also gives scenarios about the division of power in the branches of government and what happens to a proposed law, what happens when the President dies in office or Congress impeaches the President., etc.
I found a link to the book on Amazon. They also listed a workbook that I have not seen personally. The book itself is a great resource.