It wasn't me!

I picked the kids up at school, and here is the conversation I had with Yohannes:
Yohannes: Mom, today at school, someone peed on the toilet paper roll in the boys bathroom.

Me: That's not very good.

Yohannes: And that is not all.  Someone peed in the garbage can AND someone put toilet paper into the sinks.

Me: That is terrible, that creates alot of work for the custodian.

Yohannes: But that is not all.  Someone plugged one of the toilets, and the principal made an announcement that said, that as soon as they find out who that is, their family is going to have to pay two hundred dollars to get it fixed.

Me: That is alot of money.  I guess the principal was not very happy.

Yohannes: No, she wasn't.
. . . . . . . . .

Yohannes: You know what mom, I know it wasn't me, and I know why....

Mom starts laughing.

Yohannes: Mom, why are you laughing?

Mom:  Well, usually if you know it was not you, you don't need a reason. (ie. you don't need an alibi)

Yohannes: Hmmmm....... Well, I know it was not me because - I don't even go to the bathroom when I am at school.

Mom: (still laughing) Okey dokey then.