Yes, I suspect this would depend quite a bit on both the quality of the parent as a teacher, as well as the "real" teacher we're comparing against. I've seen shocking extremes in either direction, for both individuals. I might be a bit biased in one direction, as my parents (and broader family in general) are quite knowledgeable, and could easily outdo the average teacher (as a broad average over the ones I encountered - full public school education in two different countries) on just about any topic, let alone their own areas of specialty.