In a post about the value of teaching Newton’s 3rd Law from the get go, Greg Jacobs discusses how he deals with possibly accomplished students who complain having to label forces a certain way, which may seem laborious to students who “get it”.
So when the bright kid says, “Mr. Lipshutz, I know this, why are you making me waste my time writing silly extra words on my homework,” how do I react? I start by wondering why it’s such a big deal — if he knows what to write, why is it so horrible to take a moment to prove that to me? I might appeal to the idea that I want all of our problems to look similar, so that the class can help each other more easily. I might be transparent about my pedagogy, giving an impromptu Newton’s third law lecture to show the benefit.
In the end, if the student pushes my patience, the answer is, “Because you’ll lose points if you don’t. You may drop the class if you think this requirement is overly onerous.
I think the issue here for me is that such a response represents to me a subtle confusion among three things: evidence of understanding, evidence of misunderstanding, and lack of evidence for either. And I think this is where standards-based grading may come to the rescue. In a grading system where you take away points, evidence of misunderstanding and lack of evidence for understanding are both punishable offenses. Standards-based grading, however, focuses our attention to confirming evidence of understanding.
I was trying to think about what Kelly O’Shea might do in this grading predicament. Kelly, I think, would grade such a skill with a “-“, meaning that the student work provides no meaningful data concerning this students’ understanding of the skill or concept. The students isn’t punished for not labeling things the way you want them to; they simply can’t be given credit for understanding things for which they have provided no evidence. Maybe they will show that evidence later by labeling forces the way you want; or maybe they will show you evidence of understanding in a different way.
What do you all think?
What Jason Thinks: http://alwaysformative.blogspot.com/2012/06/burden-of-proof.html
Teach. Brian. Teach. 
I have a cite for this: http://homepages.wmich.edu/~chenders/Publications/2012PetcovicResSciEduc.pdf
It’s like you said, the question is on whether the burden of proof rests with the teacher or the student.
Thanks!
I’m a little behind on reading blogs.
Anyway, three answers:
1) Make the wording of the objective about what you want them to do. For example—
4.1 A UBFPM I use multiple diagrams and graphs to represent objects moving at a changing velocity.
Instead of “I can…” because this core skill is about whether you actually approach problems in that way (drawing multiple diagrams), not about whether you can approach them in that way.
2) That’s great. If there was an objective for “I can get the right answers to physics problems without showing any work”, you’d get a 2 for sure. (A line like this always gets big laughs from the rest of the students—and sometimes from the I-only-care-about-numerical-answers kid, too.) But if there were such an objective, it would certainly be a B and drawing diagrams objectives are always As. When it comes to the Bs (the “I can solve problems…” objectives), everything about the solution has to be correct in order for it to be a 2.
3) Depending on how grossly negligent the response was, it’s definitely either a — or a 1 from me (on the B objective). A lot of times when they aren’t doing something procedurally (as in dotting i’s and crossing t’s the way I want them to do) correctly it is a — from me, yes. Meaning I’ll let your previous mastery (or lack thereof) stand because this isn’t a very good demonstration either way for me. And usually kids who are doing that don’t already have the 2, so they’re going to have to circle back to it eventually anyway.