Really hope that teacher loses her job. Like seriously. Who punishes bases on accusations, does no investigations and gives a punishment to the entire class to force a confession.
The people who ran the small town USA high school I went to 25 years ago. They either outright ignored reports of bullying, and other issues, until they got so bad the papers noticed; or, they'd crack down HARD on as many people as possible at the first rumour of potential trouble.
The individual teachers were generally better than that, but the administration was trash that covered up sexual assaults of multiple students by one of the teachers for YEARS by punishing students for speaking up about it. They also never apologized or admitted they made a wrong choice.
On top of all that, students do dumb sheet all the time. The student body was almost as clique-ish and hive minded as the administration.
So, yeah. The least realistic thing about this, to me, is that the problem was resolved at all in a way that didn't end in Yukishiro being suspended for two weeks without question while Ichinosi got detention for speaking up in her defense.