Student or Learner
An instructor may interfere / transfer / impose his negative feelings with/ to/ on his job and gives an unfair grade to the students.
Thank you for allocating your time answering my question.
Transference is also the word used in psychology for this sort of thing, though usually it applies to people - transferring a feeling about someone to someone else. For example, if the instructor was angry at his own children at home, he could transfere those feelings onto his students.