  Explication and reflection on expert vs. novice considerations within the
problem-solving process characterize a cognitive apprenticeship approach for
the development of expert-like problem solving practices. In the context of
grading, a cognitive apprenticeship approach requires that instructors place
the burden of proof on students, namely, that they require explanations of
reasoning and explication of problem-solving processes. However, prior research
on instructors' considerations when grading revealed their reluctance to use
such a grading approach, motivated by a perception of teaching that places the
burden of proof on the instructor. This study focuses on physics graduate
teaching assistants (TAs) who play a central role in grading. A short
professional development activity was designed that involved eliciting TAs'
perceptions regarding grading, presenting a cognitive apprenticeship-inspired
grading rubric, followed by a discussion of the dilemma between placing the
burden of proof on the instructor vs. the student. In this context, we examined
TAs' grading considerations and approaches towards grading and the effect of
the short professional development grading activity on them.
