I just watched The Beautiful Truth with my son. Not only did he understand what uranium was, but he was aghast that someone would think it's o.k. to inject it into a human body. His words exactly, "why would they put radioactive material in someone's body?! Were they trying to blow him up?!"
You're how old and you know this?
But also, about the movie, that awesome boy was a homeschooler.
I'll bet his mother is so proud of him.