I can't believe this is literally the whole story. Sounds more to me like the black kids (because of upbringing issues) were more likely to be threatening violence with said items. Everything seemed fair until the likes of Al Sharpton jumped in.
That is most likely the cause of the “discrimination”. Those kids who were wielding weapons and threatening violence just happened to be black. So, in typical efficient gub’mint form, instead of trying to stop black kids from stabbing and shooting each other, they chose to pass zero-tolerance rules. Now no school administrator has to think at all. I wash my hands of this matter. Throw the child out. It’s the law.