I confess to having been a 'fast stream' entrant to the civil service - Inland Revenue. I was 50, the age limit having been raised because of a recruitment crisis. I was worried by the attitude of some of the 'whizz kids', straight out of university with their PhDs, etc. I had run my own business and understood the difficulties faced by many tax payers, but some of the younger recruits seemed to think their job was to get the maximum tax, rather than the correct tax. For example, I said that we should always inform people of any allowances they could be claiming, such as depreciation on equipment, and some of the other trainees took the view that if the tax payer did not know about it we should not tell them. Fortunately, the tutor agreed with me.
I was also a mature entrant to teaching, at 31, and again I was unhappy about the attitude of some of the young students who came straight from sixth forms at 18 with no experience of life. Perhaps training for some careers should not start until entrants are 25.
The ability to pass exams is not necessarily a good indicator of success in any particular walk of life.