I wouldn't rely on it.
- Will vary by cohort. e.g I scored 82 for my P.E SACs, rank 1 and 85 for my business SACs, but for P.E the exams are difficult and unseen, where as in business everyone knows the question before the SAC so my rank has been ruined. People would assume I'd be better off in business because of the higher score but thats not the case at all.
- Grade distributions change every year, minimally, but still can affect you by 1-2ss
- Also, grades are misinterpreted by many. The cutoff for a B in some subjects may be something like 45%, where as in other subjects like some maths, the B cutoff is much higher. You can't really predict by letter grades too because sometimes they have a large range. I've seen some ranges up to 20 per letter grade. A high B or low B can change your ss by a few scores.