OASC 'CANDIDATES' and WANNABES, PLEASE READ THIS THREAD FIRST!
I seem to recall talking to an OiC AFCO a while ago about this, though more to so with OR recruiting than OASC. IIRC an experimentation (but not regular use) with Cannabis (now Class C) was OK-ish but anything higher was a no-no. It was surprising how many people were being binned for thinking that XTC is not illegal, or at the most a Class C drug.
If ever having experienced Cannabis was grounds for being kicked out then my entire JOCC course are gonners, since the DAPO copper lit the corner of the biggest block of Cannabis Resin you ever saw and passed it round during his lecture. Admittedly he did watch to see no-one held on to it for too long: it was "just so we knew what it smelt like".
On the subject of DAPO, bearing in mind when I went through IOT the more generous attitude to drugs had not come into force, the following incident made us all chuckle:
Picture the scene, 80-odd IOT cadets in Whittle Hall for DAPO lecture. Copper says, "Come on you lot, half of you were students so you must have had a go. Anybody had a sniff of Hash?" Whittle Hall always had a soporific effect so I can only assume the person involved was half-asleep, but they raised their hand. 79 pairs of eyes went wide and stared in disbelief at the suicidal gesture (just before collapsing in hysterics), and one person quickly sank very low in their seat and hoped that none of the staff were present (they got away with it - just).
How we all laughed on the way to the serious burns unit!!!!!