If you collect every note from school's classes there are clues in each of them for every code but if you just want codes here is the list.

Table of Contents

Story Mode

Asakura Ayumi (this is the only you need to progress the story): 534

Aoi Takeshi: 401

Suga Yosie: 505

Tsuchiya Taiko: 377

Hard Mode

Asakura Ayumi (this is the only you need to progress the story): 865

Asakura Ayumi (this is the only you need to progress the story): 399