For other readers, I’d be curious the jurisdiction.
The specific app that can turn off iPhones requires the “unleashed” firmware I believe.
Also, regarding legality, if you are DoSing cell phones, you are creating a hazard where users are no longer able to contact emergency services, and this is the most likely avenue of charges, as opposed to FCC fines (if in USA) for using locked spectrums.
This is why attempted murder, kidnapping, etc is a charge. We do not yet have a charge of "attempted mass personal device disablement". and there is no reasonable case for......"manslaughter" of a device.
Being "realistic"/less analagous; Your mobile device is the most important inanimate object to you in every single category imaginable. And this is the case for most of humanity for some time now. If someone knowingly removed my access to my personal device maliciously, I would suddenly start caring very much about seeing that persons freedoms taken away.
Edit: after rambling I wanna reiterate my first bit....intent is 99 percent. In this case, it's a kid. The law has context, and I think they should of course be lenient.
The kid should be told not to do it again. And no law enforcement should have ever been involved in the first place. Otherwise we are teaching those children to distrust authorities, that authorities are unjust and unfair. Thus undermining the rule of law.
All their classmates are also involved and watching the outcome of the situation. Some might end up seeing the "system" as being unfair and are not going to think twice before stealing or committing some other crime, e.g. fraud.