You said it yourself Teachers are regarded as...
must teacher's also wear school uniform
You said it yourself Teachers are regarded as professionals, so they in no way must have a problem showing it. restricting certain dress code's will not help the situation they must have a specific dress code in which they can be identified and given the proper respect they deserve. Foe instance when people see a policeman they get frightened because of what he/she has on, that's the type of authority teachers most use in class rooms.