You would probably need to do Maths and Maths C (they call it maths C at my school, dunno what they call it everywhere else. Maths C is like matrices and shit) and you would need to do physics too.
In my (Australian) jobs guide booklet, this is what it has:
Air Traffic Controller: Level 5
Level 5 is:
"Most occupations in this group require the completion of a Bachelor Degroo or higher qualification. Studdy is usually undertaken at universisy. At least five years of relevant experience may be done in place of the formal qualification. In some cases, relevant experience is required in addition to the formal qualification."
Skill level 5 is the highest skill level in the book, which means it is a very hard job. Personally, in the near future, I see most of it becoming automated, and run by computers. Therefore, in my opinion, I dont see it as a very good choice unless you are the head dude who is in charge of the whole airport, which would be a realllllly stressful job