I would teach math, of course :)
I have a long answer to this question because:
- I have already given private math lessons to three students over three years,
- I am considering teaching math in high school as my plan C
- I have been told that I was very educational in my presentations
- However I have not experienced teaching to a full class sooooo I am most probably not relevant lol.
As Devalue mentioned, math intimidates a lot of people. I would even say that math traumatises half the people, and the other half doesn't see the point.
I have always thought that at the start of the year, I would make a special class in which I would explain why school teaches math, but also, the other topics.
Math: learn abstraction and reasoning, Physics / Chemistry / Biology: discover the world + how to do science on different scales; History: discover the past and the mechanics behind the creation of countries / cultures; Geography: kinda the same about the current world; and languages, well, they're obvious. (I'm probably missing a few classes lol)
Most pupils see school as a chore and as a "preparation" for the real life (for when you're 18). Actually school teaches you to be a citizen (of your country, or the world), rather than anything. You learn your job in specialised schools, not at "the" school.
Also, a big problem with teaching, is time. In general the schedule doesn't give enough time for the programme of the year. I don't know how to solve this, of course, I cannot create time. So I understand the teachers who just rush the programme and leave behind the pupils who struggle. I'd rather crop the programme, teach a bit less, so I can take maybe one hour per month to do a recreational activity to do some "fun" math
(yeah, I know) or some practical cases that's not about abstract triangles or functions, just to keep the interest. Or maybe explore a part of mathematics that's not in the programme and that I find more interesting.
Although the problem is that the interesting math is also complex and complicated, but when I see how easily I can communicate about my PhD, I believe that it's entirely possible.