Near the beginning of the movie, we find out that there is a drought and we see from the above view that all plant-life in the valley is supposedly brown. However, when Sam goes to school, all the grass and trees are bright green.
this is not a slip-up
in the scene before this when sam brings her step-mother her breakfast, she walks back in to the house and the water sprinklers turn on and sam panicks to try and shut them off, but her step-mother says no leave them on and sam says no there is a drought, and then her step-mother says its ok etc. then when sam goes off to school they show a scene of the front of the house and all the houses around their house have dead lawns cept theirs because the step-mother doesnt care about the drought [to show shes evil and wants to be treated as royalty] and has been using the sprinklers to water the front but every one else has been conserving water.