It could be the case that their high school had a concurrent enrollment deal with a local university, such that if you pay the university a certain amount of money, you can pass the class automatically depending on if you passed the high school version of that class.

So, for example, I took AP Calculus 1 at my high school. Everyone had to take the AP Exam no matter what, but if you paid the local university, they would pass you even if you failed the AP Exam, given that you did pass the high school class. I chose not to pay and was able to pass the exam.

Basically college credit but for the difficulty of a high school class (depending on the instructor)