When students make mistakes, they routinely make categorical ones with rare exceptions. Even in this active learning situation where the questions are challenging and apparently unique (compare to, say, standard 20th century physics instruction), the students' mistakes are predictable. This presents an opportunity to speed up the grading process by a large factor.

When grading a problem where the student trips over units, for instance, it should suffice to write "U" on the side, deduct whatever points you feel reflect the severity of the mistake and move on. Do not waste time writing "your units are off here" or "units wrong" or even "units." It is UP TO THE STUDENT to figure out where they were derailed, not you (though you can nudge them in office hours if they really can't figure it out).

In order for this to work, a universal code should be used and accessible to the graders and the students alike. One can even generate unique codes for specific assignments, but beware code proliferation (which starts to waste your and the students' time again) and "symbolosis": using the same letter for two totally different kinds of mistakes.

Here, then, is a list of "Universal Grading Codes" which can be used right away. We expect the list may morph and grow, but new universal codes should probably be brought up at meetings, not decided on unilaterally.