As far as I can tell, Japanese schools are way too concerned with their reputation and not enough about actually getting shit done.
A girl is being constantly bullied and the teacher is encouraging it but no one cares until the mom complains. And then they decide to only punish the main bully and go way too far.
Here, they're so worried about how that picture looks for the school, they didn't even consider the circumstances. A Suspension for posting a minor misdeamor is ridiculous.