School staff are typically advocates for children. They would have been thinking about what was best for Ethan. They would have worried about him, not just seen him as a threat. That is what is hard to understand if a person has never worked in schools, with LE or other professions where you work with children.
They didn't want to just throw him out, remember, he didn't have a disciplinary record. Maybe the counselor or someone advocated for keeping him at school. I don't know how to explain how school staff have a "heart" for children. The public hears about a kid with "bad" behavior, and thinks, throw them out! Easy! But that's not how school staff think. I had students that moved, or were expelled, and I worried about them for a long time. Teachers typically don't want to get rid of kids and wash their hands of them. If he had a long history of behavior problems, it would have been easier.
As it turns out, it was a mistake to put this boy's well being above that of others. It's a balance and the school erred on the side of his well being, IMO.
He should not have been returned to the classroom. They failed to see the seriousness of his drawing and notes. They perhaps saw it as a isolated or first time offense, I don't know. At the least, if that classroom teacher didn't feel safe, he should not have been returned.
But the parents had the power and responsibility to stop all this in the first place.