One quiet signal

Shouting over a loud room makes the room louder. Choose one quiet signal instead and teach it on day one: a raised hand, a clap pattern the children echo, a light you turn off and on.

Practise it while things are calm, like a fire drill. "When my hand goes up, your hand goes up and your voice goes off." Make it a game the first few times and thank the first table that gets there.

Use only one signal and use it the same way every time. A room learns a signal that never changes.