Whilst I could have been an instructor at the college many years ago, the 'mind set' of student ATCOs nowadays is different. In my day, you applied because you had an interest in aviation, probably you were in a branch of the Air Cadet movement, and wanted a career which reflected this, whereas now, many (note I said many not all) students are university graduates who think they deserve a high paid job, but have no prior knowledge, experience or interest in aviation.
Yes I know all the so called experts say 'it's OK you can be trained to be an ATCO if you pass the selection tests' but I'm pretty certain the proportion of trainees who fail to reach validation standard (having passed the college course with flying colours) is much greater nowadays than it was 40 odd years ago.