It’s more difficult to slowly phase out verbal prompts than non-verbal prompts. In other words, if you remind a child to do a task over and over, he may always wait for your reminder. Non-verbal prompts, reminders with no words, can be used to achieve changed behaviour and then can be phased out for more independent compliance.
This is what an educational assistant (EA) and I put together for just such silent reminders (this is worn on the wrist of the teacher and the EA):
It does seem more logical to remind someone to stay quiet without talking yourself.