Not important at all over here. technically you can fail as many years as you want, graduate with a 51% total and still go to the best university in the country.
My total average was usually ~68-70%, so a little over the average here. I became lazy as hell in hs. Skipped a lot of homework and rarely ever studied. My preparation for most final exams is reading over my notes once or twice just before going to sleep the day before the exam

I think the most I've ever studied for any exam is 2h
I guess I didn't really see the point in putting in effort when hs grades don't really affect your future and I can easily score the hs average with almost zero effort
Stepped my game up in college though, #2 of my class