In the US, final course grades are expressed in letters (the schemes I've seen are A/B/C, and A/A-/B+/B/B-). This leaves one with the interesting task of drawing barriers in between students (a task best performed at 2am the night before moving out of your apartment).
I am not comfortable with adding different components of the grade (like the midterm and final), as the average and standard deviation are vastly different. Is there a good statistical approach to this problem, with some convincing theory behind it? (Being at IBM Almaden, I should automatically go for rank aggregation, I guess... But there seems to be a lot of noise in the rank, since there are clusters of people with similar scores on each exam.)
Fortunately, if you only give one midterm (and assign low weight to the homework), you can plot the results in 2D. Unfortunately, you may end up with something like this:
Oh well... Everybody knows grades are somewhat random.