I wrote this a while go. I supervise at a school at noon hour so I am an expert, yes I am.
1. In a playground, when there is gravel (or some similar ground cover), if there is a "deposit" left by a wayward dog, rather than tell someone that there is poop on the ground so you can remove it, kids will bury it in the gravel, rendering it invisible.
2. Some kids like to pee and watch it go down the slide. We call these kids Scott.
3. Throwing up after twisting the swing around and around and around and around, and then letting it go to spin around and around and around, is common. This vomit on the ground can also be rendered invisible with the "cat- litterbox" method of covering it up.
::Note to nervous moms:: Throwing up like this is no sweat for a kid. They do it all the time, wipe their mouth with the back of their hand, wipe their hand on your pants when you go to check on them, and they are good to go.
4. In the sandbox, water, milk, juice, and ...uh...tinkle, all make acceptable sand-bonding agents for building a castle.
5. Surprisingly, swing seats with dried bird poop on them, will not be used. They are icky. Kids do have their limits. You can however flip the swing seat over, or rub it off on a nearby unsuspecting student.
6. If you are a kid on a swing, even if you have been on long enough to lose the feeling in the lower half of your body, if another kid comes up and wants a turn, you "JUST GOT ON". Time apparently stands still the moment you climb on a swing.
I may add on to this sometime soon.