I see too many people using their regular voice and expecting children to know they are in trouble or doing something wrong. How can they know unless we use a very strict voice and facial expression? Then they get it. You can't use the same voice for praise and for scolding. I see it all the time and it makes me shake my head. Poor kids. If you want 5 children to understand with a few words that it's time to listen, pay attention, walk somewhere, look out for danger, whatever the reason you need codes. I use a double hand clap when we are outside and 5 little faces pop up and look at me to see if it's time to go home or to the picnic blanket, etc. It works!