It's not too hard to get passable marks in a subject you don't understand well and then forget most it. Suppose a given class has a 40/60 applied/theory split.

It's not too hard to get passable marks in a subject you don't understand well and then forget most it. Suppose a given class has a 40/60 applied/theory split. Our hypothetical student is average in some sense and gets 75% on the theory. Now if they get at least 37.5% on the applied portion they barely pass the class. There are minimum GPA considerations, and you might need at least a C in some classes rather than a D to continue, but it's pretty common to spread the hardest classes out so that you only have one super hard class to focus on each semester, and easier courses and generals will help pad out the Ds on your transcript to maintain a passing GPA. Throw in a retake or two for a couple screw-ups, and you still graduate in 4 years with a whisper of a shadow of an ability to program. Filtering for high GPAs and whatnot can help (or it might exclude people who had family emergencies or other complicating factors and still know their shit), but in the worst case that's just a measure of the amount of time and dedication spent per course. You also probably need to set a pretty high threshold -- you can bomb all your algorithms, data structures, and applied programming courses and still have a 3.5+ GPA if you do well enough elsewhere.