Haha consistency :')
As an added safety measure at our school when it comes to "collaboration", if you have a SAC for Maths subject and you're absent on the day regardless if it's a legitimate issue or not then you'll have to sit an oral examination to explain your answers and all to a Maths teacher in case you "cheated." Likewise in English each class gets different prompts to ensure fairness (however I cannot tell if for English if it's fair or not as some topics are better than others)...
That sounds like a good idea, but surely if you have written your "working out" then there isn't much you can explain beyond that? Unfortunately due to logistics, many SACs at my school are run during different periods and days. You'd think that people wouldn't discuss the answers and questions, but it still happens regardless. Sometimes I feel like the SACs aren't invigilated thoroughly enough. There have been numerous instances in classes where students continue to write, even after the "pens down" call. 
English SACs are all held simultaneously usually in the hall. For our English SACs (Reading and Responding) we are given a list of practice SAC questions, and 1 week before the SAC we are given a list of the real SAC questions which they will pick out of a hat the day before the SAC (around 6 questions). Teachers aren't allowed to provide feedback or look at any work to do with the real questions. This is supposed to reward the people who "study". On the other hand of course, it's not a real indication of exam conditions. Only problem is, they'll use 2 questions for the SAC, reschedule and redemptions. So basically, if you miss the SAC, you automatically have 2 less questions to study for. Personally, I think if we persisted with this system, a better idea would be to add 2 questions, so there would be 6 possible questions at any one time. Oh well!