There's no doubt this teacher was a "trouble maker", but based on what I know of his case and the physical layout of the school/campus, this appears (to me) to be a bogus charge. However, if he went to trial, he would probably be accused/convicted of threatening his boss, among others. BTW, this school/campus is located in a very affluent suburb.
Plymouth High teacher pleads guilty to concealed weapon charge, will resign

