Two posters to alleviate interruptions while you teach. If a child signals by displaying the appropriate number of fingers, you can tell at a glance what they want. I've made one for preschoolers, without the pencil signal as they don't ask to sharpen them.
Make eye contact and nod yes or no. This also avoids children getting out of their seats to ask you, and lessens "copy cats." You also don't have to say a word. Simply make eye contact and nod yes or no.