I think Assassination Classroom does a pretty good job depicting actual school cliques. I’m used to seeing (western) media with student characters being separated into the “jocks”, “nerds”, “cheerleaders”, “goths”, etc. Assclass doesn’t categorize Class 3-E into labels. Rather, it chooses to show the cliques based around personality types.
Case in point, the train scene in episode 07.
Here we have the natural leaders. They get along because they’re proactive and have no problems getting serious with the assassination. Isogai and Kataoka are obvious, being the class reps. Kimura is action-oriented and the son of cops, so it he fits in well with them. Yada is mature and thinks about her future, so she’s definitely comfortable around people with strong prospects.
Next we have the easygoing extroverts. Not actually immature, but prefer to have fun and engage in interpersonal activities. Nakamura and Maehara are social butterflies that like to fool around. Okano hangs with them because of her boyfriend she likes friendly competition. Okajima and Kurahashi are playful types who share a what-you-see-is-what-you-get personality. And Fuwa, who would seem like an introvert, is actually really outgoing and fits right in with these thrill-seekers.
Then we have the clear introverts. Reserved and prefer to keep to themselves, but have no problem with others who can share in their interests. Sugaya and Mimura are the artistic types, and can engage in passionate discussions with one another. Chiba and Hayami, the hardcore stoic duo, clearly enjoy each other’s company and fit right in with people who can give them their personal space.
Following up are the anti-social students. They can engage in social interaction, but actively reject society’s expectations of normalcy. Terasaka’s posse of Yoshida, Muramatsu, and Hazama are the “delinquents” who get along easily because of this. Takebayashi clearly prefers to be alone, and most likely hangs around these guys since they can respect his individualism. Hara is the one woman out, and probably connects with the group due to her friendship with Yoshida.
And finally, we’ve got the wild cards. At first glance, you wonder how such differing personalities can get along so well. I believe it’s partly a friend-of-a-friend type of situation. Karma is an old friend of Nagisa, who is best friends with Sugino, who likes Kanzaki, who is admired by Kayano, who is friendly with Okuda. But also, they each have a nice balance of playfulness and seriousness that they just sort of gravitate to each other.
This is the type of school I grew up in, and it’s nice to see a representation of that in my favorite anime.