Yes i agree that the 6 week stint can effect your whole career, someone off a previous course was borderline in a check. When his personnel file was looked at the unit manager said "your attitude to the 6 week OJT course was not very good" and this was one of a few reasons as to why he got the chop.
Your attitude can effect you throughout your training from catc to the initial posting. SO watch what you do and what you say!
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ATCOs do it at the top of buildings!