Same with ATCO. The 'lesser brethren' were posted to low intensity/complexity units (our grading system) to consolidate, find their feet and hopefully move on and up. Others went to more intense/complex units, where they would be able to cope as an ab-initio ATCO. Some even moved straight on to Area Radar training, although at that time it may have been partly a manning requirement!
The various air/ground systems were quite sensible. There's no point in putting people out of their depth, and failing, after time/effort/expense has been committed to training them.