Can relate to all this myself too. Very imaginative, day dreamer type. An “Around the day in 80 worlds” sort of person.The comments sections of my school reports would be all glowing with praise and “untapped potential” but my grades never reflected the comments. With zero revision i blasted through my exams with little trouble though (the ones we do at 16 in the UK). It was at 16 to 18 (We call these ‘A’ Levels (Advanced)) i just got bored of school and my A level grades bombed. Total shock to my teachers as they expected me to go on to great things. My A level physics teacher was encouraging me to go and study theoretical physics at university! lol
Having the inattentive type of ADHD meant i too slipped through the cracks and was never diagnosed in my youth. I guess a diagnosis at 38 is better late than never!
Good Luck james 