I had a transient stay in a commonwealth country when I was a teenager. I "gave" a few A-level exams. I.e. I studied on my own and just showed up for a grueling exam organized by the British Counsel in my country. I picked the subjects that were easiest for me to study on my own ... Econ, Accounting and General Studies. Since I didn't take A-level math, I had some trouble in college (in North America).