Hillsdale College has free courses. If your kid is smart he/she should be able to handle it Id think. Especially if you take the course as well and can discuss with your child. The concepts remain the same no matter what age level a kid is at.

They also give out a free pocket Constitution and sell them in bulk fairly cheap. Ive bought hundreds of them and donated them to schools and librarys in my area. I also leave them on the table at weddings and funerals and birthday partys and such.