You have to wake up pretty early in the morning...

So, as a form of incentive, I give out what I call Math Money.  The kids "earn" it by doing what they're supposed to do and lose it by cursing or breaking other rules.  I mention cursing because unfortunately that's the most frequent offense.   (Perhaps I should be thankful it's not something worse.)  Anyway, this Math Money is what constitutes their participation grade.  They must turn in $15 every week and I collect it on Fridays.  

Obviously with such a liquid asset, there's always the threat of money being stolen from my desk, or wherever else I thoughtlessly leave my stack.  That happened early in the year.  I was out sick (it was a legitimate sickness that time) and the substitute was letting them run wild (as is usually the case) and someone in one of the classes stole a stash.  I know exactly who does their work and who answers questions, so when some knucklehead (yes I did have to look up how to spell knucklehead) turns in a wad of dough, I know there's a good chance it's stolen.  

I didn't want the hassle of calling anyone out and trying to get the money back, (it never works) and I wanted to make it clear that I don't play.  Also I had in my drawer about 50 sheets of copied money that I didn't want to waste.  So, I told everyone that because one of their classmates had stolen from me the money was no good and that they may as well throw it out.  Some of those faces were SO disappointed, but I put on my stone face and when anyone gave me money I threw it in the trash.  Then I got out a red smile stamp that I happened to have and stamped all the new money.  From then on I would only accept money with the proper red stamp.

Months passed before I ran into this little situation:

The one on top is the authentic Ms. Johnson Approved dollar. The one on bottom was what remained of the counterfeit after I ripped them all up.

The girl who brought them (like $13, that's a big deal) to me is not the type you would expect.  She must have had these dollars stashed for 5 months and she cleverly found a smily stamp.  Sadly it wasn't one that looked like mine.  She was also sly enough to mix them in with actual money.  When I confronted her she obviously feigned shock.  It was the kind of shock that you can tell is fake.   This may have worked on an ordinary teacher, but she didn't know who she was messing with.  Nothing gets past me.