When you need your grade-schoolers attention say in a loud voice: "One, Two, Three - eyes on ME!" Teach them to immediately respond in unison with a loud: "One, two - eyes on YOU!" After their response they should know to be quiet and attentive. Follow up can be verbal: "I see Jailen's eyes... I see Brianna's eyes..." etc.
Thanks for the tip Mrs. Rorick! =)