When Sylvia was a first-year, the teacher for her first Transfiguration class never showed up. Instead, a tabby cat sat on the lectern. Whether she had grown bored of waiting or for some other reason, Sylvia and her deskmate made a cat teaser themselves.
Since the girl from the Muggle world did not know Animagi existed, nor did she know that Minerva McGonagall, Head of Gryffindor, was a registered Animagus, she was not docked any points. Still, she became the subject of gossip for the following year.
Everyone had been young once. The Weird Sisters were far "safer" than Voldemort, and besides, children always needed a common topic. When everyone else was doing something, not joining in made you seem like an outsider. It was like everyone knowing how to swim except one person, or a girl during Prohibition refusing to go out with a boy who could not drink, or everyone in the Hippie movement wearing bell-bottoms while one person wore a shirt and tie. It did not matter if he was a teacher, but a fifth-year student dressed like that would be mocked by his peers.
The winds from outside the school always blew into it, like the radiation cloud from the Chernobyl incident in the rumors, and the Wizard Purist Party's resurgence in Europe because of it. The headmaster had no time to deal with such matters.
Pomona got headaches, palpitations, and shortness of breath from that heavy metal rock. But since her House had a Metamorphmagus Animagus who constantly strutted around before her with pink hair, she could turn a blind eye to the Weird Sisters shirts.
Students came to school to learn how to control their powers. Tonks should have been able to use hers properly rather than letting her hair change with her moods.