Well, the actual scores you receive don't really mean anything - only your ranking and position in your cohort matters. If everyone is consistently doing poorly or the average is really low, then that is not necessarily bad. This is because after your SACs are finished, its essentially school vs. school, i.e. your SACs scale depending on how your cohort performs in relation to the state. What I mean by this is that, if your school's average in a particular subject is, let's say, 40%, but then everyone smashes the exam and scores A+'s, then the SACs will scale up accordingly.
Also, if you're doing poorly in SACs, more than not, that will probably reflect in your exam performance at the end of the year. So I'd recommend thinking about why you're not doing as well as you want, and then take action to rectify that.