I can say without doubt or shame that this is the best thing i have ever witnessed... until chapter 81.. after that, then is just not prison school anymore, the atmosphere of joy and suspense is not there, that is a shame because this was a masterpiece (in the beggining) , then is trash.
Even so, this manga is a must read, you just have to toss away the last part, i am not exaggerating here , Hiramoto Akira destroyed what the character were, just don't go further after the good chapters, is a slap to the face what the author did to the reader.

Story - 10 funny, ecchi, creative.

Art - 10, it was a great artwork.

Characters - 10 I enjoyed them all

Enjoyment - 10, I could't stop reading

Overall - 10

Obviously all of this taking away the whole fiasco after chapter 81