How heavily does Education impact your job?

Hey guys,

I'm currently still in the Australia/Canberra equivalent of high school, but my grades are 80-85% on average,
I study for stuff, and work a lot on it; but struggle to do well. Probably because I don't pay for tutoring.

I want to go into IB, and be very successful in my career, but at the current rates of my grades; I'm not
first in class. I want to run with flying colors, but all I can do is grind through work and hope I improve, or find
an alternative solution, which I haven't done yet. I'm interested on how far in the future I should be worrying about this,
I know that high-school will inevitably lead to University, and if I do poorly now, it's a long term disadvantage because
it accumulates.

So, how did/or do you think education plays into your career? Is it just something that helps, but not essential to be fantastic, or is it a perquisite to the job (with the path of least resistance) to be a brighter student?