There's a few memorable quotes from the movie...
Here there are :

[Arriving at the school, Mathieu sees a small boy waiting by the gate]
Clément Mathieu: What are you doing?
Pépinot enfant: I'm waiting for Saturday. My father is coming to collect me.
Clément Mathieu: But it's not Saturday today.

---

Chabert: Action. Reaction.

---

Clément Mathieu: You see evil everywhere.
Chabert: Here? Yes.

---

[Chabert is dragging a boy off for punishment]
Clément Mathieu: What are you doing?
Chabert: He stole my watch. From my room.
Clément Mathieu: Where are you taking him?
Chabert: Dungeon.
Clément Mathieu: Wait!
Chabert: Why?
[Chabert and the boy disappear into the school]
Clément Mathieu: He's my only baritone.

---

Pépinot enfant: I don't know any songs.
Clément Mathieu: Well, I'll teach you some. For the moment, I'll name you assistant choir master.

---

Pierre Morhange: What about the solo?
Clément Mathieu: Which solo?
Pierre Morhange: My solo.
Clément Mathieu: Oh. Your solo. No, there's no solo. You don't have a bad voice but no-one's indispensible.

---

[Morhange's mother has come to visit him]
Clément Mathieu: [quietly] I didn't tell her last time that you were in detention, I told her you had a toothache and went to the dentist. Don't tell her I lied.

---

Violette Morhange: Do you have children?
Clément Mathieu: No. Well, yes, I have 60.

---

Clément Mathieu: [they've found the stolen money and a harmonica] You know Mondain was expelled because they thought he'd stolen the money.
Corbin: No, sir.
Clément Mathieu: No, that's right you didn't. But now I've told you. So what were you going to do with this money?
Corbin: If I tell you, do you promise not to tell anyone?
Clément Mathieu: Promise.
Corbin: I was going to use it to buy...
Clément Mathieu: To buy what?
Corbin: My Montgolfier balloon.

---

Clément Mathieu: [Mathieu finds Pépinot sitting on the stairs] What are you doing down here?
Pépinot enfant: I don't have the right to go upstairs.
Clément Mathieu: What do you mean you don't have the right?
Pépinot enfant: I don't have any money.
Clément Mathieu: What?
Pépinot enfant: I'm not allowed to go upstairs unless I have some money.
Clément Mathieu: Says who?
Pépinot enfant: Mondain.

---

Clément Mathieu: [some of the boys are hitting Morhange] Hey, why are you hitting him?
Pépinot enfant: Because Morhange threw an ink bomb at you.

---

Rachin: [firing Mathieu] Go to the devil!
Clément Mathieu: No. I'm leaving him behind!

---

Pierre Morhange adulte: Pepinot was right all along. Clement Mathieu was fired on a Saturday.

---

Clément Mathieu: [talking to Mondain] Sing!
Mondain: You won't like it.
Clément Mathieu: I don't care sing!
Mondain: Okay...
[singing]
Mondain: One Summer, I took out my nob, and gave myself a nice handjob...
[inhales as if to sing another line]
Clément Mathieu: [interrupting] Enough!
Mondain: [smiles and chuckles] Hmph!
Clément Mathieu: Baritone.
Mondain: What?
[gives Mathieu a look of surprise and confusion]
Clément Mathieu: I'm not making fun of you, you are a baritone....
[Mondain still confused]
Clément Mathieu: .. it means you sing in a low voice.


I think i am crazy for this movie... Haha!