Ok so I am going to put down which subject is for which character, (as it doesn't say anywhere here or in game)
Biology - Kazuki (pink haired boy) (my precious cinnamon roll!)
English - De Quincey (blue haired girl)
French - Lyon (white haired guy)
Chemistry - Nanami (brown haired girl with the hat)
Math - Robin (black haired boy)
Physics - Hattie (other girl with (light) brown hair and no hat)