I have done pair programming with a junior partner, and I found it extremely beneficial. Taking the time to talk out my ideas and logic invariably helped make them clearer in my mind and realize pitfalls much sooner than I otherwise would have.
I had to explain things clearly and logically, and he was bright enough to ask good questions and point out typos as I was coding.
They actually still do bloodletting, and even use leeches to do it.