For future reference..

..when you have munchkins of your own someday, and want to know the lazy person's way to effectively deal with them. (All derived from my experiences watching over the 4-6 year olds at the French-American School. They don't work as well on my little cousins, primarily because I'm family and they don't understand French so I can't fall back on that.)

Playtime
Scenario: The children are throwing rubber balls twice the size of their heads at each other.
What you say: Children, no! Do not throw the balls at heads or arms or legs! You may only throw them at the chest!
Reason: Kids have awful aim, so if they aim for the chest, they usually end up hitting the stomach, where there is lots of baby fat still protecting them. Thus, it hurts less. Any other parts are more suspectible to harm, which results in crying, and crying must be avoided at all costs.
Outcome: This works really well, because they're still allowed to attack each other, which keeps them out of your hair. You know you've taught them well when you hear them yell at each other, "Aim for my chest, stupid!"

Fights
Scenario: Child A has called Child B a crybaby.
What you say: Do you think you're a crybaby?
Reason: Because Child B usually is a crybaby, but you can't really agree with Child A now, can you? But this question makes Child B think about it for a little and usually confuses him/her, and very often, staves off the tears.
Outcome: Usually, Child B will just say "no!" and resume playing. If s/he starts crying (this is a likely outcome also, unfortunately), see "Crying," below.

Crying
Scenario: Some prima donna of a brat didn't get his/her way and lets everyone know by fully demonstrating his/her lung capacity.
What you say: Go find the maîtresse and tell her what happened.
Reason: Well, you're not the one really in charge, are you? No, you're just the assistant.
Outcome: You have diverted the crying one away from you. Otherwise, you get a little runny-nosed teary brat sitting on your lap whom you have to spend a good half-hour consoling as she (because face it, it's usually a whiny little girl) chokes out, "He... he... he took my .... jump rope, but I.. I... " You get the idea.

Drawing time
Scenario: Child wants you to draw him/her a picture of something, say, a butterfly.
What you say: So what do you think a butterfly looks like? Why don't you show me?
Reason: You're too lazy to draw and help them out. Plus, this fosters creativity.
Outcome: Be glad, you have enabled a future Picasso to practice his/her craft.

When the child wants something
Scenario: Not content with markers/snacks/racing cars/paper airplanes, the child wants you to do something for him/her.
What you say: En français, s'il te plaît?
Reason: This is a French-American school. The kids are technically supposed to speak in French, and this way you're helping them practice.
Outcome: You get to sit on your lazy ass for another few minutes as the child tries to figure out how to make his/her request in French. Sometimes it takes awhile and they forget what they even wanted in the first place.

Note: These might not seem as though they'd work, but said with a smile and a tone of childish conspiracy, they do. And the other teachers look upon you with awe as all your little children seem to be extraordinarily self-sufficient and well-behaved while simultaneously having fun. Plus, the kids love this sort of tough love. I have all sorts of pictures they've drawn for me up on my fridge as proof of this. Minimal effort for maximum results. However, when they start declaring that they only want to play with you, you know you're too good at this.