Based on what we have seen in other high profile trials and events it is entirely possible that what the prosecutors have said turns out to be entirely untrue. Think of the Zimmerman or Rittenhouse trials, or the many news reports of MAGA hat wearing attackers who beat up Jesse Smollet.
Even if it is true, the school officials should have acted on the information they had if they really believed the kid was a danger to others. They could have simply sent him home, or called the police, or called an ambulance to have him taken for a psychiatric evaluation. They didn't though, so at the time they must have believed that it was safe to let the kid back into school.
The media and the prosecutor want to blame the parents because the mother tweeted out support for President Trump. Notice how nobody is asking for Darrell Brook's mother to be arrested for not keeping her son away from the car he drove through a parade.
“Even if it is true, the school officials should have acted on the information they had if they really believed the kid was a danger to others. They could have simply sent him home, or called the police, or called an ambulance to have him taken for a psychiatric evaluation.”
I can’t imagine a school calling an ambulance to send a kid for an involuntary psychiatric evaluation—especially after the parents apparently said there was no problem.