What is the meaning of [When the cat is away, the mice will play]

This is a very old proverb, dating back to the sixteenth century. It means
that when the person in authority is away, those under him will take advantage
of his absence.

> ‘We had a simply marvelous time at school today. Mrs. Brown was in bed with
‘flu’, and poor little Miss Smith can’t keep order for nuts!’

> ‘When the cat is away, the mice will play, right?’