Fond de l'Etang is a boarding school for troubled boys located in the French countryside. In the mid-twentieth century, it is run by  The principal, M. Rachin.

M. Clément Mathieu, a middle-aged man. new supervisor to the school. Mathieu does not believe in the "action - reaction" policy. Slowly, Mathieu's approach of trying to match the discipline to the crime does have a positive effect on a handful of students. With the reluctant approval of Rachin, Mathieu begins a grander experiment of trying to transform the overall atmosphere within the school, core within the experiment being to start a choir among his students. This move is a difficult one for him as a failed musician, as well as for the initially reluctant students.

Pépinot, a younger boy, seems to lack guidance and focus, and who always says he is waiting for Saturday when his father will pick him up, he who never does. 

Pierre Morhange, an older student, is the anachronism: introverted, but prone to outbursts of individual subversiveness - the devil with the face of an angel as the other teachers describe him. Behind the reason for his subversiveness, which Mathieu slowly learns, Morhange hides a love of music and a true talent in it.

M. Rachin, The principal in the Fond de l'Etang school,who was an egotistical disciplinarian whose official unofficial mantra for the school is "action - reaction", meaning that there will be severe consequences for any boy out of line. 

references:
http://www.imdb.com/title/tt0372824/plotsummary?ref_=tt_stry_pl