This movie (Buta ga ita kyôshitsu) is Japanese children’s take on capital punishment, although it is on a pig they raise. An extract from IMDB:

The most special scenes are the 5-minute and 15-minute real-time, documentary-like and thought-provoking classroom debates in which students spontaneously discuss if they should eat the pig. While shooting the two scenes, seven cameras operated at the same time. Besides, the debating scenes were not rehearsed. Only given partial scripts without lines assigned to them, students had to discuss the issue with their own arguments, which makes the movie authentic and distinguishable from other typical animal movies. The debating scenes shot in a documentary-like style also remind me of The Class, a French movie with non-scripted classroom discussions.

By the way, the official website link displayed in the trailer is down. They did not renew the domain.