Did your teacher say what should be done in order to get an S? I know for my school you had to do some sort of redemption task (like a resit) or prove you've done your homework.
I'm clutching at straws here, but what is the average of the sac? The pass rates for my sacs for chem were 15%+. I remember last year one of my sacs I received somewhere in the mid-30's, but the average was around there as well (sacs were hard af). My teacher said that on the final exam, an E grade was somewhere around 20% (if i remember correctly), so why should you need a 40% on your sac to pass?
I really don't mean to scare you, but I've heard that if you receive an N on a unit, you might get kicked out, consequently leaving you with 1 less subject (but this is like the extreme worst case scenario)
It really isn't the end of the world. I remember last year when I went to my Further maths lecture, the lecturer said that if you didn't do well in your sacs, it's you're time to shine for the final exam (which is true, since it's worth 60% of your grade). I have always abide by this saying.
All the best