bpi
Your story is not uncommon. I know at least two other jet captains who found school totally uninspiring and left with the school thinking they were not capable of achieving anything special. Clearly intelligent, which the school was not able to unlock.
What they both had was an absolute passion and determination to commit aviation.
They both went back to night school to get the maths (sums) up to speed.
CPL exams first, followed by the ATPL Nav block, as was pre JAR/EASA.
FI route to hour build. The rest they say is history.
The modular route has a lot to offer, and invariably produces a far more rounded individual. Integrated customers who commence training towards their mid twenties have life experience which is also invaluable.