This is a wonderful film. Its moving, slightly sad, and heart-warming. I watched it first at school with my GCSE standards French, in French, with French subtitles. Although I didn't understand all the details, I still enjoyed it immensely, and however you watch it, it is amazing. I had the song "Les Choristes" in my head for days.
The film begins in the future, and then is mostly a flashback. A new teacher arrives at Fond D'Etang, a school for difficult boys, to teach music, and immediately discovers the harsh discipline and the bad behaviour which forced the man he is replacing to retire. His unusual methods soon warm the boys to him, and he achieves a lot. There is some wonderful music, especially the soloist, Pierre. Pepinot, a very young boy, is adorable, and he partly gives the film its touching ending.
Whatever standard your French is, even if you watch it in English; whether you like this sort of music or not, you cannot fail to love this film. It's hard for me to put my finger on what exactly makes it appeal so much to me, but the characters are probably its best feature. They are well developed, lovable (or hatable, in the headmaster's case) and they make the film stick in your mind. Make sure you give this a try!