This is a tried and true poster to reach students at their level so you have less phones and electronics interrupting your classroom.
The poster (on a stop sign shape reads) TAW PTOYED in "texting language."
Translation: "In English: Teachers are Watching, Please Turn Off Your Electronic Device. Sincerely, Your Teacher."
Electronics are a part of life. Students should understand the rules of your classroom. You set the tone. Phones interrupting class can ruin your lesson. Let them know you understand "texting."