Any 17 year old who can take on and endure such a huge responsibility has learned far more about life than what wasn't taught him in those missed days. The mother has raised a terrific son it sounds like with FAR GREATER VALUES than what the so called public schools have to offer. This is where rules made to discourage truancy go way too far and common sense is nowhere to be found except for the 17 year old.
If the son can’t be excused for caring for his mother, that
would imply that classmates could also not be excused, i.e.
they could not spell him for some of the driving, etc.
Think about what that teaches them.