I really appreciate my Greek teacher. In Monday's class, she was explaining some phenomenon, I forget which, and uttered the sentence: "In Latin [whatever it was] is different, because the propenultimate [second-before-last] syllable can never be stressed." This is, of course, nonsense: In Latin, either the penultimate or the propenultimate syllable is stressed; it is the ultimate syllable that is never stressed. This is probably what she means, I thought to myself, as did most of the others, I suppose, as we're all taking Latin as well. No one, not even I, felt it necessary to correct her, and she went on. I figured it was a slip of the tongue -- I certainly don't doubt her Latin, which is at least competent, and promptly forgot all about it.
This morning in Greek class, she was there early, writing up some tables and forms to be used later in today's lesson, as she always does. In the corner of the whiteboard, though, was the following sentence: "Correction to ridiculous mistake: the propenultimate syllable can be stressed in Latin (e.g. obLIvio, CIcero)." And in smaller print "it is the ultimate syllable that's never stressed".
She must have realized her mistake while making it, or shortly thereafter, or some time after class. The point is that although she knows we all have enough Latin to recognize it for a slip of the tongue and not be confused by it, she felt responsible for uttering nonsense in class, and chose to make explicit her recognition of that mistake.
I admire this behavior with all my heart. This is good teaching ethics, in my book.