I seem to have misread your post on your parents' responses and apologize for my accusations of ambiguity. I also applaud the format of your test with the students; you got the information you were looking for in a context that completely disguised the question while at the same time getting the information that your lesson to the children was about. However, I stand by my contention that *logically, it's wrong to say that the antepenultimate is third from the last, but then who am I to condemn something linguistic for not being logical?

As a further test I would suggest asking people to identify the first from the last in a series.