Chemistry Credit
It sounds like this person had a guardian angel looking after him, and this guardian angel was sent to help him graduate high school. According to this person, he didn’t take chemistry, but he somehow got a chemistry credit – and that’s the credit he needed as a prerequisite for multiple classes.

This mysterious chemistry credit is what eventually allowed him to graduate. It almost sounds like too good of a coincidence. It must have been a clerical or bureaucratic error, but it was like a godsend for this person. We just have to wonder if this gap in chemistry knowledge somehow affected his other classes.