I can't remember much about the manga but here it goes -
I know that the main character (uke) comes to a school and there are a bunch of weird kids in his class.
I think one of them is a foreigner otaku who is obsessed with Japanese culture and figurines.
Another one is scary and hides in a make-shift shelter, he also threatens anyone who tries to mess with the teacher. I think I remember he is older than the other students because I think that he and the teacher went to school together. In fact, I think I remember there being a short story about them in the manga.
I really hope I'm not mixing two mangas up together and making a whole new story! Sorry that I'm being so vague - my memory is not very good! Thanks to anyone who can help! 🙂 ))

Well, if I'm not mistaken it should be Ossu! Ren'ai Gakuen

Yes this is it! Thank you so much 🙂 <3