He picked up a gun, brought it into the school, showed it to people and didn't turn it into the office.
This doesn't warrant a mental evaluation IMO, but it isn't quite as innocent as "any kid who picks up a gun for any reason".
I'm slightly skeptical that the kid actually "found" the gun on the bus. The authorities may suspect that he BROUGHT the gun to school on purpose and thus, a mental evaluation is the result. That, I agree with.
The entire driving force behind all of this are the lawyers. If the school doesn't check out the child's mental status, then the school is liable for what happens next. However, in almost every case, the school can tell you who is dangerous and who's not. Again, because of lawyers, the school can NOT indicate that they think a child is dangerous because of liabilities. So, it is the perfect catch-22. The lawyers love it because it creates case after case for them. Lawyers ARE the primary problem and are the REASON society can not make the correct judgements and act upon them. The greed of the lawyers = the end of the nation.