>

That must be a US-specific thing.
I know Canadian parents may claim the front office does nothing, but provided everyone does their job, this is not a thing.
goddamn,  sounds absolutely premeditated.  
"Two days before the shooting, the boy allegedly “slammed” Zwerner’s cellphone and broke it, according to the claim notice. He was given a one-day suspension, but when he returned to Zwerner’s class the following day, he pulled a 9mm handgun out of his pocket and shot her while she sat at a reading table, the notice says." >

Well, yeah, he brought a gun. 
I wonder if there were any risk assessments done for concerning behaviour? 
That’s what would happen in a Canadian school. >

So here's what we learned from other articles:
- another student warned the front office about it because he had shown bullets to other students before he shot her
-the teacher warned the office about issues after the phone was taken, the front office said "it's end of day so nothing we can do"
-the parents claimed the child was in a program and was supposed to be in the class with him, but wasn't that day. 
-parents claim the gun was locked up...(qustionable). 
So basically there was a lot that wasn't done, but there was a lot of warning. >

That part about the front office doing nothing checks out. In my brief time working at public schools several kids engaged in violently disruptive behavior and the general response was - handle it yourself.