Have you ever attended a martial arts class when the head instructor was away? This happens a lot in the bigger schools, but somewhat infrequently in the smaller ones. I’m always interested to see how the students respond when the master is away.
The unfortunate aspect of a class being led by a substitute, almost assuredly a junior ranking teacher, is that some members of the class simply won’t work as hard. That would be bad enough if it weren’t also the case that these same folks seem to want to disrupt the entire class. They groan when asked to execute strenuously, or they talk out of turn.
These wanna-bees miss a fundamental element of the class.
The hard work, the exercise, the effort is not for the benefit of the instructors; it’s for the students. If you find yourself working harder when the master is in the room, versus when a junior instructor is leading the class - take note, you are the one who’s missing out.