dotted rhythms, dot dot dot

Tonight I was teaching a Beethoven Sonata to a student and almost corrected him on a rhythm. Luckily I double-checked before I actually said anything because it turns out that he was playing the right rhythm and I was the one who had learned it wrong - so many years ago!

So am I a good teacher because he knew to play it right, or am I a bad student because I had learned it wrong in the first place?