Something similar happened to my son (who is also ADHD on the Spectrum) in 2nd grade. He took a cuticle trimmer to school. It was one of those with multiple cuticle tools that folded out of the device. The whole thing was only 2.5" long. It had a little pair of clipper scissors that folded out of one end and tweezers on the other end.

But, the third tool that folded out was a cuticle "knife" about as long as the end of your thumb. It folded out on the side. It didn't even have a sharp edge. It was more for levering the cuticle up to get at with the little scissors. It was also extremely tight in there because it had never been extended until that day.

He was caught with it while using the little scissors. The teacher's aide who examined it wrestled the "knife" bit open. Then, I was called in with a claim he'd brought a pocket knife to school.

I was incensed when I saw what they were calling a "pocket knife." He was the kid who'd just raised more money than any elementary student in the county for AHA ever (a record still not matched to my knowledge). He'd never had any aggressive behavior. Never said unkind things. Went out of his way to be helpful. The teacher had even told me he was "an amazing little person."

The school counselor and academic counselor pointed all of that out in the meeting. The school acknowledge it all. Still, they suspended him for three days because of their "no tolerance policy" crap.