I would say the school certificate matters to some extent as it is a good indication of skill levels and strengths/weaknesses that could be used for future subject selection. It is also great to see how you compare to the entire state. But, as a number of people have said, it is okay to stuff up; it is merely a kind of stand alone test that often lets the naturally smart and highly skilled people excel.
By the way, what is a 'good mark' - I am in the top maths, english and science classes and I believe for my skill level (moderate) band 5s (hopefully mid-80s) is a fairly good band but band 6 for maths (my strength) ?? I try really hard but often lack important skills and find it hard to grasp certain concepts.
Please reply, thanks y'all...
Oh, it is good for me that I do the school certificate tests as I am already on holidays! Yeah!