Other mistake: Annie is the only teacher in the town, and there is only one classroom with students, all who are around the ages of 10-12 years old, even though the schoolhouse she teaches at is a two-story, mid-sized building with multiple rooms. There are no administrators, staff, custodians, or other teachers and no students in lower and upper grades at all. Even when Annie and Melanie are evacuating the children during the crow attack, there is only the two women and Annie's students. There is no-one else.
Other mistake: It seems well established that the film takes place over a weekend. However, Melanie drives up on Friday, stays at Annie's apartment that night, goes to Cathy's party the next day, Saturday and stays at Mitch's that night. Nowhere in the movie is it implied that she stays another night and in fact she doesn't. Everything else in the movie after the attack at Mr. Faucet's farm takes place on Sunday and there would be no school in session when the children are attacked.
Other mistake: When Melanie is signing the card for Cathy on top of her car there is a brown paper bag underneath the card, she leaves it, when she drives out it's no longer there.