Deliberate mistake: When Mary gets to the school where she is going to be teaching, all the children are standing outside wearing shoes. However when they come in to the school they are barefoot. I have a feeling this was done to show how poor the community she was teaching in was supposed to be, but it looked like too cold and rainy of a day to let the actors be outside barefoot.
Deliberate mistake: The house is in a field with no lights around it and should be dark at night, but during exterior shots at night, the house is always lit up on the outside and the interior shots always show very bright lights coming into every window (much brighter than when shown from the outside). There would not be lights that bright shining into the house during that time period. Obviously, just an effect so viewers can physically see the house and characters talking.
