There is danger in not having in place a formal mechanism for students to request a re-marking of a piece of work. The following situation has occurred: A student visits the faculty member during office hours with a marked test. The student has altered an answer so that it is now essentially correct. There is some initial banter between the student and the faculty member. What went on here is the issue, but it can never be conclusively discovered what was said, given the informal setting. The faculty member begins to look at the particular answer, initially believes that the answer as shown deserves more marks, but then discovers irregularities that lead her to believe that the original marked answer was altered. The faculty member tells the student that he has submitted forged or altered material for academic consideration; the student counters by saying that he did not ask for a re-marking -- he merely wanted to verify that the answer as currently formulated was correct. He said, she said, without an easy resolution.
Without trying to affect the free exchange of ideas, the faculty member should establish some clear mechanism for students to request a re-mark. Perhaps a cover letter, with points to consider, along with the entire piece of work in question, within some reasonable time frame after the piece of work was initially marked. The policy could say that the entire piece of work may be re-marked, and the final mark may go up or down. Do the re-marking “off-line”, not then and there in front of the student. Still allow students to come to office hours and chat away about ideas. But as soon as the talk begins to approach the correctness of a marked answer, apologize and invoke the mechanism.
Alternatively, ask the marker to put a tight “box” around the answer being marked, so that nothing can be added inside the box after the fact. Ask the marker to explicitly indicate what is right and what is wrong with the answer as given, to discourage any alterations. If the answer space is left blank, ask the marker to put some obvious visual signal that the space was blank, like a large Ø. Ask the marker to use a broad-tip red marker (like a gel pen or a Sharpie ®) with ink that “leaks”, not an ordinary ink pen. Never allow students to write in red or in pencil if they want their piece of work re-marked.