When I was in graduate school in the 1970s, you couldn’t teach in Ohio with a degree in history unless you went back to school for four years and got a degree in education. High school teachers were often people with a degree in secondary education and a minor in a subject, and there was no guarantee you would be able to teach that subject. If a school had three math teachers and three history teachers and needed to lay off two teachers, it was perfectly legal to lay off two of the history teachers if they had less seniority (or encourage them to take early retirement if they had the most) and move the math teacher to the history department. My high school biology teacher was from a foreign country. He was originally hired to teach English, but he didn’t speak it well enough and drew protests from parents when he assigned “Brave New World,” so the following year the school made him a biology teacher. Nowadays, things are different and you can order papers on  http://domyhomeworkonline.net/ for a writer proficient in one field of study.