A friend of mine left a high-tech career in mid-life to work in mathematical education. In September 2000, just before the school year began, he called me: There is a project to promote mathematical education in elementary schools; come join. The project was in a development town called Maalot, in the far north of Israel. (Israeli development towns, built in the 1950s to settle new immigrants, are usually considered to be rather backward.)
I am a professional mathematician and, although I have been strongly interested in teaching (which is the reason that my friend had the idea of offering me the job), I had not set foot in an elementary school since I was a child. So I consulted whomever I could. The advice I got was uniform: Don’t do it. Elementary math education is a profession in itself. There is no connection between it and teaching math at the university level.
In hindsight, sobriety should have dictated listening to this advice. Yet, had I listened, I would have missed one of the most fascinating adventures of my life.