Please try to avoid being poisoned by your own cookie dough recipe. =)
FearfulSymmetry: But I don't want to scare them off too badly either. That's bad for my image. :) Although the idea of messing with their minds is fun ...
I'll have you know yoga is suited for pretty much anybody as long as you start out easy. :P But I can imagine that not everyone is attracted to it.
Okay, option two - Wait for them to complete the course, then give them a small gift. When they ask why you're giving them a gift, just say that you'd heard things didn't go well, so you wanted to cheer them up.
When they ask who mentioned it, just become very apologetic and say that you shouldn't have mentioned it at all.
They'll either be confused, and the slow erosion of their confidence can begin, or they'll be under the impression that those evaluating them are commenting aloud that they're doing a bad job.
Either way, it works against them, and it'll just be you trying to console them after poor performances if anyone wants to observe the situation.
It's not that I wouldn't at least be willing to try. I'd just need an empty room, for the sake of not traumatizing anyone who had to bear witness to the display.