IMHO
I make it a habit to practice purging and switching regulators, clearing mask, locating my octopus,
and adjust straps. I this way I am creating muscle memory, hopefully should an emergency arise
I wont need to think about a solution. Teaching such repetitiveness to a student "might" pay higher dividends then say yanking off his or her mask during a pool session.
I’ve seen student divers in a quarry step of the platform with the tank valve closed! THIS SUCKS, or more correctly DOESN’T SUCK, air that is.
But then again after thirty years hunting with the same buddy we still ask each other to check our safeties.