I have seen so many of these posts the past few weeks or so, and they pop up every year. Heaps of people at school come onto ATARnotes to search and ask the exact same thing, but if you look at other threads you will see the question has been answered before! But to re-iterate what most people tend to agree on:
If you do bad in your first sac for example, say you get 70%, that score in and of itself doesn't exclude you from getting a 50, because when it comes to sacs your ranking is the most important thing. If the rest of your class did worse than you, then you should be alright with getting good marks in the rest of your sacs and still getting a 50 or close to, but there is another point to consider - If you don't go to a particularly strong school, and you get a 70% or something on a sac and you're not clearly ahead of people, you really need to think to yourself whether you can get a 50 or not. Big result changes from 60 or 70% to 98% require big changes in things like study habit and stuff. I have seen countless people doing psych or further in year 11 and they say to themselves and everyone "Oh I want a 50, I will get at least a 45", then they just get 70's on sacs and the exam and end up in the 30's. When you haven't done VCE yet it can be hard to gauge what work and scores are needed for correlating study scores, but the people I know personally who have gotten super high scores (over 48), were all meticulous and hard working and from the first sac they knew what was going on and got A+'s.
A 70% in a SAC I think really shows that you didn't know the topic well and maybe didn't try hard enough. If you knew all the content and had prepared well enough by doing practice sacs etc. but the sac just went really badly (a rushed long answer question didn't go your way, missing decimal points, misreading something etc.) you would still get over 80% most of the time. The 70% really shows that you don't have that strong knowledge of the topic, and when exam time comes around, it could hurt you. I know it did for me and other people - our worst sac topic was the area we did poorly on on the exam. If you want a really high score you need to learn what you got wrong and really step up your game for your next sac.
The low score itself isn't the disqualifying factor, but it is the reasons you got that low score that would hinder your final mark. There are always exceptions though, and this is just another thing to consider that is so often overlooked.
TL;DR "I did bad in a sac or two, are my chances of a good score ruined?" No, but take a look at yourself and your study habits and look at why you didn't do well. "They just didn't like my definition" or "Oh I just forgot to do those last steps" aren't really excuses if it was so drastic you didn't get an A or higher, you can study for these things and that is what practice sacs are for.
Good luck with your studies and never give up ! Let a bad sac score motivate you to smash the rest of them !
P.S my word is not final, you might disagree, these are just things to consider that I have noticed from my peers/predecessors/fellow AN users