The characters:

Name:Park Chan Yeol

Personality: Cheerfull, goofy and playful 

Class:2OA

Name: Byun Baek Hyun

Personality:Hot tempered, Hard working, Childish

Class:2OA

Name: Kim Jun Myeon

Personality: Know-it-all, protective, Gentleman

Class:3EC

Name: Kim Jong Dae 

Personality:Joker, Attention seeker, get's offended easily

Class:2OA

Name: Zhang Yi xing

Personality:Unicorn, mind allways somewhere else, Hardworking, always smiling

Class:3EC

Name: Kim Min Seok

Personality: quiet, pessimistic, clean freak

(don't misunderstand Xiumin is my second bias)

class: 3EC

Personality: Arrogant, Curious, Lazy

Personality: Helpfull, On the quiet side, Super scary when he snaps. 

Personality: Never-had-a-girlfriend-yet-they-are-all-he-ever-think-about, Shy, goofy

(yep that's jongin.) 

Minor Characters:

Personality:Talkative,Shy and calculative

Name: Huang Zi Tao

Personality:Hot-headed, Spoiled and lazy 

Class:2OA

Name: Lu Han

Personality: Sporty, Boyish and flirty.

class:3EC

Name: Wu Yi Fan

Personality: Mysterious, Bad temperament and possesive

class: 3EC 

Name: Lee Chae Rin

Personality: Independent, Bossy and charismatic 

Class:3EA