It's funny how, as a student, your teacher seems like a real adult person from a completely different generation. But I guess after you fast-forward a few decades, the difference becomes pretty trivial.
EDIT: I misspoke & meant "I don't know how many kids have just a 15 year age gap with their teacher". Not sure why this was flagged though.
The point I was trying to make is that it's generally rarer in the US/Canada for a teacher and student to only have a 15 year gap. Tenure rules for unions & generally increasing class sizes means there's comparatively few new teachers entering the profession straight from college. Younger teachers also have a high attrition rate because of pay, the difficulty of the job, lack of support across the board, dealing with parents, etc. Having just a 15 year age difference with a teacher that continues to be a teacher and mentor in your life throughout for an extended period of time from then on seems extremely rare these days. So I was trying to provide color why the statement "It's funny how, as a student, your teacher seems like a real adult person from a completely different generation. But I guess after you fast-forward a few decades, the difference becomes pretty trivial." may be overlooking differences from when this relationship was formed.
I'd stay it's probably a pretty low ratio somewhere around 1:10 or 1:20, but yeah a lot of them don't stay teachers for a long time, but that's still more than enough time to make impressions on students. And I'd bet there's a very high correlation to making an impression on a student (in your first few years teaching) and staying in the profession.