Shorts of Ansatsu Kyoushitsu (TV) 2nd Season which adapt chapters of the manga which are not in the TV series. The adapted chapters are 78 ("Takebayashi no Jikan") and 79 ("Shihaisha no Jikan, Ni Jikanme"), which are published in the ninth manga volume.
AniWatch is the best site to watch
Ansatsu Kyoushitsu 2nd Season: Kagaijugyou-hen SUB online, or you can even watch
Ansatsu Kyoushitsu 2nd Season: Kagaijugyou-hen DUB in HD quality. You can also find
Lerche anime on AniWatch website.