It is the perfect echo of a teacher who taught them how to kill him, and in doing so, taught them how to live.
That specific episode (Season 2, Episode 25) is titled (or similar, depending on the fansub). It is the series finale of the entire show. Assassination.Classroom.S02E25.Future.Time.1080...
It seems you’ve referenced a file title: — likely an episode of the anime Assassination Classroom (Ansatsu Kyōshitsu). It is the perfect echo of a teacher
“Now then, class — let’s begin today’s lesson.” and in doing so