EXOD847 The law "You shall rebuke, yes rebuke, your fellow" [Leviticus 19:17] applies to all instances in which you become aware of a wrong and have reason to believe that your words can make an impact. Thus a teacher should admonish a student who was acting inappropriately, and a student should rebuke a teacher in similar circumstances: "How do we know that a disciple sitting before his Master (who is judging a case and) who sees that the poor man is right, and the wealthy man wrong, should not remain silent (if his teacher is wrongly favoring the wealthy litigant)? Because it is said, 'Keep far away from falsehood'" [this verse, see Shevuot 31a].