During its first season, Ansatsu Kyoushitsu (Assassination Classroom) was considered one of the best. It ranked 4th in the TOP manga sales of 2015.
The first live-action film premiered in March 2015, and the second will premiere in the spring of 2016. The manga ended in March and had 4 spin-off chapters about Koro-sensei's vacation.
I expected the same success in the second season; I wanted to see the students' development, new dramas, their relationships with the teachers, and the prejudice from the rest of the school. That's not quite what happened in the anime, and my disappointment started in the first episode when it didn't show Koutaro Takebayashi leaving Class E and going to the main building.
The way this happened, how it was exploited by the principal, and the reaction of Class E were important because they profoundly showed how they want the class to be seen by the other students in order to reinforce the principal's idealism about how education should proceed.
Takebayashi was quite expressionless, and after this event, he gained a fundamental role in subsequent events. This wasn't shown in the anime, and nothing was explained, not even in a narration using Nagisa.
Everything was happening at a very fast pace, missing small details that provide the basis for both the humor and the action to be developed. Losing some of the context, the anime has been somewhat bland and is losing ground on "best of" lists. Perhaps they want to move quickly to the arc where the mysteries are revealed and end the anime this season exploring the most tense and decisive part.
Even though the anime didn't reach its full potential in the first part, from episode 15 onwards, the series entered a new arc with a new opening. This arc will conclude the anime. You could feel the change in atmosphere; the revelations made it clear how serious the matter is and made you think about the future of Koro-sensei and Earth.
Taken from the blog: Kimiko no Nikki