Dustin Hoffman seriously studied the piano in his youth, but was not considered talented enough to make a career of it, just like his character Master Carvelle.
Days before filming in Texas, Garrett Wareing (Stet) broke his left arm in three places, shooting all of his scenes in a splint, and having it cast after filming wrapped.
According to extras on the set, namely members of the real Boychoir, Dustin Hoffman was horrendous at conducting in real life. So much so that a real conductor had to lay in front of him - off camera - and conduct the Boys properly. Apparently Mr. Hoffman has no rhythm.
A planned Spring 2016 broadcast of the film on CBS was cancelled at the last minute after a backlash from real-life former choirboys who were sexually abused at a private school similar to the one depicted in the movie.