This article was particularly interesting to me because my mother has also gone back to school. She is not studying Computer Science, she is studying law. The question of whether or not older students can learn OOP really is asking two questions: 1) Can older people successfully go back to school? and 2) Is OOP so revolutionary an idea to people that have already coded before that they cannot grasp it?
In order to examine the first question I can use my mother as a reference. Students who are continually and exclusively in school can devote all of their time to the perfection and mastery of their studies. Older students have families, jobs, and other things that tend to distract them. It is not easy for my mother to work at home so she has cram all of her studies into the 9-5 day while she is at school. That plan actually works out well.
But students of CS are very different than those of law. As we all know, the law changes pretty frequently. In order to stay on top of the new laws that have been passed since the lawyer went to law school they need to go to refresher courses once a yea r. Similarly, the students in the OOP class are attempting to stay on top of their field. But unlike CS, in the law, when a new law is made and needs to be understood it is as simple as explaining what the law is and some examples of why it was put into place. OOP is not as easy to explain.
The assumption here was that many of the students had already taken C or another proceedural programming language. The transfer from proceedural code to OOP is not an easy transition to make. It requires that people think of coding and designing in an e ntirely new way. It is like adding a new dimension in the reality that we know as home. I know it sounds a little flaky but that is how "new" I consider OOP to be.
But I think that the article clearly demonstrates that the old coders can learn new tricks. Not only that but they can do it with other lives as well.
I think that you let the notion of people going back to school cloud your views on the paper. Nothing was truly justified by the paper; (see Danah's paper about the faults of the methodology). I don't mean to be crass but the analysis was based on very, very SKETCHY data. There are good ideas there, but that study was lacking any substantial research.