If someone received OWLs and NEWTs in a certain subject(s) at Hogwarts, then got a job, if they decided that they wanted a career change but needed OWLs and NEWTs to do so, would it be possible for them to go back to school to get these OWLS and NEWTs? (Ex: A Wizard who worked at the Leaky Cauldron who wanted to be a healer.)
Is this even allowed? Or are you stuck with a decision you made at 15? If this is allowed, would they go back to Hogwarts, some sort of adult wizarding school, or a wizarding school abroad?
I suspect that there is no canon evidence or examples mentioned (as the case of Hermione going back to school to get her NEWTS is a special case) so well-argued speculation is warmly welcomed.
Some of the answers and comments from: Is there wizarding education for adults? were helpful but didn't answer the whole of my question: if you answered or commented on that post please feel free to elaborate on your answer or comment in relation to career change and retaking examinations!