I have never seen any school in UK or South Africa anywhere where instructors do not wear a white or blue shirt and black or blue trousers be they teaching CPL or PPL. I've instructed at three schools and flown at around 20 regularly either whilst training or since some based at international airports others at small fields.
Every instructor who taught me wore a a flying suit or a shirt and tie and most usually bars too.
I think it embarrasing that people would not want to wear a shirt and tie and call themselves professional pilots.
I feel it essential that the public can differentiate instructors (myself included) not only by bearing, manner etc but also by uniform. If you want to wear a polo shirt then go and be a life guard at the local swimming pool, or play polo.
I expect my doctor, lawyer, dentist, banker, etc to wear a tie and they do. Hey even the guys stacking shelves in Waitrose wear a tie how an earth can any professional feel that it is acceptable to not wear a shirt and tie.
It is this sort of pinko lefty softly softly american rubbish that is leading to the changes in society today that are less than desirable.
Sorry just had to sit on the fence for that one
So that'll be the pin pulled.