Crap like this has been going on for at least ten years. There have been stories nearly every month about some kid getting in trouble for drawing guns, bringing a toy soldier holding a toy gun to school, pointing a gun-shaped chicken nugget at a fellow classmate, having an ax in the trunk of a car, having a butter knife under the seat of a car, pointing a finger and saying 'bang', and having an accidental explosion in chem lab.
Educators, unfortunately, are not the brightest among us. Add to that the fact that schools have insane zero-tolerance policies because of teachers' and administrators' inability to use common sense, and it's no wonder stupid stuff goes on all the time.
The kid in this story may very well be guilty. There's not enough information available to tell. But if he's innocent, he and his family should sue anybody involved. Yes, you can sue individual law enforcement officers if they violate your civil rights.