My teacher one year gave me an F because he didn't bother to grade anything in a timely fashion, also didn't store (or organize) any student assignments that had been handed in, and when the end of the year came made me go digging through a giant stack of everyone's assignments to find mine to prove I deserved a reasonable grade AFTER I had already been sent home with an F. I eventually got the grade I deserved, but I shouldn't have had to fight for it like that. Apparently this was a common routine for this teacher, but lots of students didn't bother to fight it. It didn't get fixed until that cabinet was physically emptied and I handed all the assignments back to their authors.

I am thinking of the teachers. And I think OPs situation is remarkably similar. But kids, being kids, will not be heard by adults when they shout warnings, like "Why haven't you graded and returned any of my assignments yet this term?" or "This valuable/dangerous thing should be secured, who responsibility is that?" It may not be moral advice, but like the song says, sometimes you have to be cruel to be kind.