It is forbidden to relate to a member of a community, family or organization that someone spoke cynically of his group; to do so is to speak rechilus. This is true even when members of that community, family, or organization regularly joke about themselves. It is common for people to poke fun at themselves, yet be offended when others make similar comments.
The same applies regarding a school. Students who regularly joke about their school or class are often offended when outsiders make similar comments. Therefore, mentioning to students that someone spoke negatively of their school is speaking rechilus.[It should be noted that joking about one’s own school generally involves loshon hora or at least avak loshon hora.]