In situations where reproof is required (see Day 93), one is obligated to interrupt even his own parent who is speaking loshon hora and respectfully explain that he or she should not be speaking in this manner. A rav, as well, should not be allowed to speak loshon hora. However, it is disrespectful to accuse a rav of speaking loshon hora. Instead, one should ask the rav for assistance in understanding why it was permissible for him to make a given statement.
Children are not included in our obligation to reprove a fellow Jew who has sinned. However, parents, as well as teachers, are obligated in the mitzvah of chinuch, educating their charges in proper mitzvah observance. Thus, parents and teachers must train children from an early age to refrain from speaking or listening to loshon hora.