My dad left school at 15. He was in a big family and limited money so it was the norm at the time.
Same with my father. He was academically bright but the family needed the income so he left school at 14 to be a tea boy on building sites. Luckily, his brightness showed itself and he was sponsored by the firm to go to night school and qualified as a surveyor.
My mother only had a basic education, left school at 16, was forced to go to secretarial college by her parents but dropped out after a year and got a job doing filing and the like in an office.
I stayed in school until I was 18, in spite of hating every minute of it, barely scraped through my O levels and failed to get a grade good enough to reach third level. I have several IT-related qualifications and, after a mid-life career change, am currently studying for my final exam in my current career in financial services.
My brother dropped out of school as he hated it, did an apprenticeship as a carpenter and now runs a rather successful construction company.
My nephew is half way through his degree in civil engineering so looks like being the first one in our family to complete third level.