Your DS' behavior in the classroom is a problem for the teacher, and he has drawn a straight line between the behavior and the results. It appears to me that you think that there's no relationship, because this should be easy... too easy, in fact, which would explain why he's behaving so badly in the first place. The conflict is, the test results line up with the teacher's theory, not yours.
If the teacher is incorrect, something else is going on with the results. To find out either way, I recommend you ask for copies of his tests so far this year... especially the 14/37 one.
You already hinted at one possible explanation... is the teacher marking each test question completely wrong if your DS didn't show a step? Was the answer still correct?
It's also possible your DS is frequently making a common mistake, and the teacher isn't spending the time to figure out what it is, and address it.
In any case, you need the data to make an informed analysis.
