  Teaching assistants (TAs) are often responsible for grading in introductory
physics courses at large research universities. Their grading practices can
shape students' approaches to problem solving and learning. Physics education
research recommends grading practices that encourage students to provide
evidence of understanding via explication of the problem-solving process.
However, TAs may not necessarily grade in a manner that encourages students to
provide evidence of understanding in their solutions. Within the context of a
semester-long TA professional development course, we investigated whether
encouraging TAs to use a grading rubric that appropriately weights the
problem-solving process and having them reflect upon the benefits of using such
a rubric prompts TAs to require evidence of understanding in student solutions.
We examined how the TAs graded realistic student solutions to introductory
physics problems before they were provided a rubric, whether TAs used the
rubric as intended, whether they were consistent in grading similar solutions,
and how TAs' grading criteria changed after discussing the benefits of a
well-designed rubric. We find that many TAs typically applied the rubric
consistently when grading similar student solutions but did not require
students to provide evidence of understanding. TAs' written responses, class
discussions, and individual interviews suggest that the instructional
activities involving the grading rubrics in this study were not sufficient to
change their grading practices. Interviews and class discussions suggest that
helping TAs value a rubric that appropriately weights the problem-solving
process may be challenging partly due to the TAs past educational experiences
and the departmental context.
