Okay, so if you've been paid for by an airline to go away on a course through sponsorship, then I guess you would wear a Batman suit if that was the requirement.
If you are spending your own money though, then as long as you are reasonably presentable, and comfortable in the your own clothes does it matter? You are there to learn - your dress sense isn't going to make a difference to your learning ability. You are the customer at the end of the day.
As with WX Man, I dressed casually during training, but presented myself smartly for the Examiner. The school I trained at said they wanted me to feel at home, relaxed and to enjoy my time with them. I did, and passed.
Uniform wearing will come with the future airline / instructing job whichever comes first.
