I agree with MON. And, in my house (or anywhere I am in charge of a group of kids), the kid who clamors for the biggest piece gets the smallest piece, (or gets to choose last), the kid who is obnoxious about being first gets sent to the back of the line etc. They seem to learn pretty quickly that it is in their enlightenend self-interest to be gracious.
We do the same thing. It works well for us.
Participating in team sports also has worked well for DD11, who can be quite competitive. She's probably a 90th percentile athlete, so she's good but not the best, and has some room to work and improve. She's also learning that the team does better when everyone works together.
