The short answer is yes.
The Advanced Subsidiary (AS) level is the same as a South African Grade 12/Matric. It’s also recognised by the SA Matriculation Board (UMALUSI) as the equivalent of Senior Certificate subjects (NQF4), which you’ll need to get into university. If you’re 16 or older, and you’ve completed either International GCSE or Grade 11, then you can take this course.