According to The Directory of American Philosophers, 1980 edition [0], he taught at Franklin and Marshall College at that time. Probably with a little more digging, you could come up with his academic CV. The school is a small, expensive, private liberal arts college that's (currently) well-ranked in the US News rankings[1].
So, what's the likelihood that the incoming freshmen at Franklin and Marshall (a) had trouble with "cats/cat's/cats'" and (b) hadn't written any papers in high school?
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[0]: https://books.google.com/books?id=5D9AAQAAIAAJ&focus=searchw...
[1]: https://www.usnews.com/best-colleges/franklin-and-marshall-c...