Who was having the Happy Time?

Yuan and Wei's essay tuition teacher requested their class to be cancelled during the past school holidays, to be replaced later.  I forgot about this, and found out that there was a tuition class today, which was not the usual day.
Me: Why is there a tuition class today?
Yuan: Because during the school holidays, we were having a happy time. But, actually, I don't know who was having the happy time, us or the teacher.
Me: (speechless)