As a wet-behind-the-ears newbie, I feel I must defend my partnering choices during class.
There are a few techniques that I am quite comfortable with. When going over those, I'm comfortable partnering with anyone in class.
When there is something new, or I don't quite understand how it works, I chose some one who does understand and can adequately demonstrate.
It's not personal. But I don't learn and my partner doesn't learn if neither one of us knows what is going on.
Or maybe I'm just a snob ;D