Ah teenagers
Honestly when I saw this, I felt most people in this movie was stupid. First off the boyfriend's dad is a douche. I mean firing someone then saying stuff like "With that attitude no wonder no one will hire you" or "Is this how you raise your kids?" after the daughter got arrested. The boyfriends parents come off to me as stuck up.
As for the girlfriend's family: the mom was okay, the dad was okay but the daughter... How many girls keep secrets to themselves? Almost all teenage girls when I was in school would tell their girlfriends everything! "Yeah I saw my bf with the teacher, Mrs Hottiepants." "He told me this, and that" When the girl followed her bf and saw him with the teacher, she didn't pull out her phone and film or take a pic? I would have. If I thought my bf was cheating on me and I was following him, I'd be on the phone with the friend sending her photo text. Also in this day and age, girls would have posted the pic online or the video online. Or if they wanted to be modest, show the pic to the parents and principle.
The teacher: seriously some sort of psychopath. I wonder what made her go crazy as a kid and kill the blonde?