Actor, co-producer Gérard Jugnot mortgaged his Paris apartment to help finance the film. The bet paid off, and he ended up making over 5 million euros for 'Les Choristes' as actor and co-producer. He earned the title of the highest-paid French actor in 2004, overtaking Jean Reno and Gérard Depardieu.
As Rachin enters the car and leaves with his family towards the end of the movie, crew members are reflected on the car windows. A man with a cigarette in his mouth can be seen (at around 1h 30 mins) reflected first in the front side window and then in the back side window as the car drives past the camera.
When the now-bandaged Maxence shows Mathieu around on his first day he shows him a wall with photos of the school benefactresses and the motto "Labor improdus omnia vincit" which is attributed to Virgil. But the second word is incorrect - it should read "improbus". Translations vary but it means something like "Persistent hard work conquers everything."
During the auditions, Mathieu sends pupils to the right or to the left showing the direction by his hand. When directing Ricoeur, who sings "I've got tobacco in my pouch", to the left (at 33:06 to 33:07) he first moves his hand to his right, which some cite as an error while others cite it as a flourish, but then sweeps or hooks his hand left.