A BKSB is an assesment used in high schools (at least my high school) that assesses where you are in math/english out of 5. I believe the general idea is that by the time you finish year 12, you should be a perfect 5 in both, 4 in y11, 3 in y10, etc etc. Most TAFE courses require year 10 levels of things which matches with a 3 in BKSB. I think that’s how that works, anyway. But TAFEs don’t use BKSB, they usually devise their own LLN assessments or buy one from another company I guess