This voice levels poster is used in most preschools during my placesment, I think it is an effective way for teachers to control the voices in the kinder. Child also remember the colors and related voice levels that they should use inside and outside.
Idea-Quiet Critters - when you decide it's important for students to be quiet, pass out the quiet critters. Take them away from students who talk. At the end of the activity anyone who still has a quiet critter gets a prize, point, whatever you use.