Not defending the school districts' actions completely here, but schools have pretty limited options when it comes to dealing with violations of law that happen online--and if the sharing doesn't occur on school grounds during the school day those options diminish even further. As soon as you, as a school or school district, try to regulate student behavior outside of that time window you end up getting sued by the other end of the spectrum. I don't know the full details of the case (and it's not clear to me here if the accidental discord was at school or not at school), so I have to reserve some judgement.
With that big caveat out of the way, the district still screwed up big time by not reporting to the police. We had a sextortion ring that we became aware of at our school (we're in a relatively small district, just one small-to-medium sized high school), which was not operating at school. That being said, because we became aware of it, our principal held an assembly with every kid in the school at once, explained what was going on, explained exactly what our response would be to any reporting that was done, and encouraged any victims or people with knowledge of the situation to come forward and meet with either admin or counselors. Within two weeks we had two perpetrators identified and reported to police and the other participants so scared that it ended pretty quickly.
