Assuming that you mean the APS referring to college/ high school subjects, it goes as follows:
There are a total of 8 levels on the APS, starting at 0, 2, 3, 4, 5, 6, 7, and 8
an 8 is a score of between 90% and 100%
7 is between 80 and 89%
6 is between 70 and 79%
5 is between 60 and 69%
4 is between 50 and 59%
vice versa...
and a 0 is between 0 and 29%