How to figure out which child is tampering with pet food

What people tried

Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.

1. 1
   Setting up a camera or spy cam by the bowls
2. 2
   Moving salt and sugar out of reach
3. 3
   Putting all children responsible for cat care until it stops
4. 4
   Sitting both children down to explain the health dangers to the pets
5. 5
   Asking students anonymously via homework assignments or sticky notes to name the culprit
6. 6
   Imposing collective punishment or taking away class privileges until the behavior stops
7. 7
   Offering extra credit or candy for private tips
8. 8
   Blowing a real whistle or joining in to annoy the class into speaking up

In their words

Unedited, most upvoted first, each linked to the thread it came from.