Pilots can come from any variety of backgrounds because the training you receive is thorough and specialized. Math and engineering courses may help, but are not necessary. The most important thing you can do in high school to make pilot training easier is to develop good study habits, whatever the class is.
I have been flying in the military for 7 years and I took general electives in high school, and studied business in college. I did not have any trouble, at least not more than the average student, in pilot training. In fact, I have not noticed any correlation between the level of skill in a pilot and the subject of their college background. Some engineers had in-depth knowledge on specific aspects (e.g., aeronautics, electrical, etc) of being a pilot, but did not necessarily increase their general piloting skill.