A levels and GCSEs show that the student is capable of studying and passing exams. It does NOT pre-suppose initiative and common sense, whereas common sense pre-supposes a degree of intelligence.
Which do you feel is more important to a prospective employer, all other things being equal? Whilst education is important, numbers of exams passed IMHO are not. Will he be an aviator, or just a pilot?!
Research your prospective employer and see just what they are looking for.
Hope it works, fellow flying person!
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Always look on the bright side of life...