DD missed four points in completing her "health" class (required for graduation) this term.
FOUR.
Three were because of badly written questions (one of which is unmistakably verifiably WRONG) and the other was because she was just plain reading too fast. She completed the entire class in just three days.
Four points. Have I mentioned that?
This was sufficient to drop her grade from an A+ to an A in this course. Really not kidding.
Ohhh.... that would make me NUTS... lol. Sorry to hear that happened... how frustrating!!
Honestly, scoring 10% sounds more like guessing than like making careless errors, and I might be more inclined to see it as non-compliance than as a work technique issue - but it depends on a lot else so I just throw the thought in for you to see if it chimes.
I wondered that myself... it's either that, or lightening fast sloppy work resulting in mass error, or flagrant non-comprehension and that just doesn't fit at all.