Hyouryuu Kyoushitsu, Eden no Ori Recommendations
The setting of a group of children which are thrown in to a dire situation and forced to fend for themselves in a harsh new environment is similar as is the themes centered around school and comradeship.
In both mangas there's a catastrophe and the kids need to get organized in order to survive a hostile environment. There's betrayal, suspicions, murders, monsters... (prehistoric animals in the case of Eden no Ori) in both mangas. Drifting Classroom is an old classic manga and it's focused more on horror than Eden no Ori.
[*] - Class of students mysteriously disappearing from earth's surface.
[*] - On an unknown place with monsters.
[*] - Survival manga.
Main differences is that Hyouryouu Kyoushitsu has primary school students and they usually stay at one place meanwhile Cage of Eden has highschool students and try to discover the land.