You heard of an national scheme called 'Skillsfuture' ?
do what u like
do what makes u happy
If you want to expand your academic knowledge, I think you are better off learning yourself via online resources, pirated textbooks, youtube, quora etc. Focusing on A lvls only give yourself a pretty limited scope of knowledge.
Personally I agree with qdtimes2, that it is better off not to focus only on A level content. The content is pretty outdated, and quite limited and basic. Content knowledge is also not the main skill for A level students.
Also, it depends on which subject matter.
If your interest is in Physics, I could recommend you more things to read up on :)
Personally, even though I specialise in teaching O/A Level physics, and both Junior and JC Level Singapore Physics Olympiads, there are still many things about Physics I have yet to read up and understand.