Many movies have that dialogue indirectly or indirectly.
Melanie and Felicia wanted to be friends with Emmaline again.They thought about that for many times and discussed together.Sometimes they would lose attention during class and the teacher would give them detention and they/she has to stay one hour extra at school after all classes are done.That means they will be alone at school.No teachers no students...only ghosts...so scary...ow.
It will be evening not night but still...fear will be there no matter when and where.
Their parents are informed by staff teachers.They are told by the respective class teachers.Parents come at that time that is 1 hour late.Children should stay in their class.They can do anything.