Of all the non-math degrees that there are, I would expect that Physics would be the very next best thing for teaching mathematics, if for no other reason than because of physics' privileged position when it comes to mathematics (http://en.wikipedia.org/wiki/The_Unreasonable_Effectiveness_... and the intertwined history of physics and mathematics.)
As a counterpoint, I have a degree in Computer Science, which I personally consider to be a slightly "vocationally oriented" field of mathematics, but I am currently reteaching myself trigonometry that I should have learned in highschool. The math that I needed for my degree I still have down pretty solidly, but for the most part the mathematics that is taught in high-schools I am fairly rubbish at. I currently would have no business teaching a high-school mathematics course; I could probably get through the lectures but would be completely unable to help any student that actually had an interest in mathematics.
A physics guy teaching highschool mathematics seems perfectly reasonable to me. A linguistics guy though? Ehhh...
As a counterpoint, I have a degree in Computer Science, which I personally consider to be a slightly "vocationally oriented" field of mathematics, but I am currently reteaching myself trigonometry that I should have learned in highschool. The math that I needed for my degree I still have down pretty solidly, but for the most part the mathematics that is taught in high-schools I am fairly rubbish at. I currently would have no business teaching a high-school mathematics course; I could probably get through the lectures but would be completely unable to help any student that actually had an interest in mathematics.
A physics guy teaching highschool mathematics seems perfectly reasonable to me. A linguistics guy though? Ehhh...