Set expectations with visual cues. Students know when it's appropriate to ask to use the bathroom and when they should wait. Print color or black and white versions, also included are versions with "emergency" instructions in each color variant.
Can be printed back to back and laminated, add a magnet to easily flip from one side to the other in the middle of teaching.
Green side "You may use the bathroom without asking"
Red side "Please wait to use the bathroom"
Optional Red notation "You may use the bathroom signal if it is an emergency"