When Donna cleans out her locker, she wears a pendant that Sharon comments on. It then shows her leaving the building, and she is inexplicably not wearing it.
When Brice breathes from the makeshift inhaler, there is a trickle of blood going down his face when seen from the side, but not from in front.
At approx. the 21:17 mark, Mitch is telling everyone to get on the bus. Although Mitch is heard saying "go, go", his mouth is clearly not moving.
When Donna gives Mitch mouth-to-mouth she does not pinch his nose shut.