In the Harry Potter books a grading scale has been established for students taking their O.W.L.s (Ordinary Wizarding Levels) and here on Hogwarts Express we also use this scale for N.E.W.T.s (Nastily Exhausting Wizarding Tests). This scale is as follows:

O - Outstanding
E - Exceeds Expectations
A - Acceptable
P - Poor
D - Dreadful
T - Troll

The first three scores are considered passing, the last three failing. It is standard for students to take nine OWL level classes (7 core and 2 electives) and two to three NEWT levels. You may not take more than 9 OWLs, or exceed 5 NEWTs without a general application.