[hn_throwaway_69]

This often doesn't work and backfires. The school will just warn them, the target will be characterised as a snitch and it will just strengthen the bullies' mutual loathing of the target.

Generally the only way to stop bullying is to build resilience and fight back.

There are extreme cases where I agree it should be reported, including infliction of physical violence.

[Ekaros]

Then sue them for not doing anything. Or start a rightful social media and media campaign so it cannot be ignored. Get them fired. This is clearly a situation where adults failing to do their job should get their careers ended permanently.