No no no, they didn't know that it was a school because they're incompetent, but ALSO knew it was as school because they're evil.

You seem to be confusing everyone's stances (incompetence vs malice). Some people in this thread believe it was incompetence and therefore not a war crime, and others believe it was malicious and therefore a war crime. I personally don't think stupidity is a good legal defense but what do I know.