There are some qualities that are close to objective - it's very difficult to find someone who thinks a majority-opinion 8/10 is a 4/10, for instance, or vice versa. But then the smaller details are more up for grabs. When it comes to those, I think it is largely a matter of individual judgment: some people have high standards and others lower; some people like one style and others a different one; some people enjoy reading what they want to hear, while others are more open to new approaches and ideas.
Classroom teachers are more prone, in my experience, to marking based on what they wanted to read, whereas assessors simply can't have expectations that rigid - marking work from across the state gives you such a variety of approaches it's virtually impossible to apply the same standards and formulae as you can in your own classroom.
Essentially, I think you need to take the marks you get in context of the person giving them, and the environment in which they give them. Does your teacher seem to prefer one style over another? Does your teacher have flexible standards or rigid ones? Does your teacher see good work as still faulty, or faulty work as still good? Does your teacher like whipping you in SACs or encouraging you? Does your teacher have a track record of agreeing with the final exam results or differing from them? And so on. None of this invalidates the mark they give: it just informs it. By knowing the person giving you the mark and feedback you're simply making yourself better able to assess their strengths and weaknesses as measures of performance.
Upshot: totally depends on the teacher.