Alitte DS is similar. He loves Maths and is vaguely considering it as a possibility. I was OK at Maths at school but I went to a liberal arts college (US) where we had to do two maths or science courses. Because my school had done an intensive Calculus course in 12th grade, I was stuck doing two intermediate college maths courses. Discrete Math almost killed me. I actually loved it, but only understood about 10% of it and very nearly failed it. 
DS is completely torn about what he wants to do so am hoping S5 gives him more clarity. Depending on the day he wants to:
Go to St Andrews to study either Maths, Philosophy or Chemistry.
Go to Cambdrige to study Philosophy and then become a teacher.
Study Maths, Philosophy or Chemistry somewhere and then do a law conversion course.
A bit odd as he definitely wants to end up in the US.
Study Maths and become an Actuary.
Go to an Ivy (Dartmouth might suit seeing as he loves St Andrews so much) and decide on major later. This would suit him well if he doesn’t decide on a specific direction over the next year! My gut says to do undergrad here and postgrad in the US (particularly if he is looking at Law and long term in the US!) but I’m swithering...