How can you tell that Barack Obama has been a university professor?

From a New York Times interview:

I want to emphasize, though, that part of the challenge is making sure that folks are getting in high school what they need as well. You know, I use my grandmother as an example for a lot of things, but I think this is telling. My grandmother never got a college degree. She went to high school. Unlike my grandfather, she didn’t benefit from the G.I. Bill, even though she worked on a bomber assembly line. She went to work as a secretary. But she was able to become a vice president at a bank partly because her high-school education was rigorous enough that she could communicate and analyze information in a way that, frankly, a bunch of college kids in many parts of the country can’t. She could write —

Interviewer: Today, you mean?

Today. She could write a better letter than many of my — I won’t say “many,” but a number of my former students at the University of Chicago Law School.