Let the kids pick names for their teams and help them make and color a team flag. Hang the flags on the walls.
Now, instead of having to address 12 children individually, you can address 3 - 4 kids at a time by calling out their team name (e.g. "Top Blade Team line up!") Also, by making privledges depend upon team behavior, the other students in the team will help their ill-behaved teammates behave.
I find that the children to quickly develop strong feelings for their teams and a certain amount of team pride.
Very helpful.