In the scene where Mia and Jamie are in the car at the school dance and they are smoking pot, the cigarette in Mia's hand changes positions along with her hand in between shots.
Lola tortures Brent by drilling a hole in his head, intending to lobotomize him. Based on the sound effects, the drill penetrated his skull. The drill would have reached his membrane and ruptured several blood vessels in the process. Brent should be bleeding a lot more than what is shown in the film.
Australian Formals have a strict dress code for any students attending. Mia would not have been allowed inside with the outfit she was wearing, which was a very thin, short and skimpy one piece dress.
Lola walks barefoot on the road as she prepares to go kill Brent's mother and Holly. Based on when the film took place (near the end of the school year during spring), Lola would not have been able to walk on the concrete without burning her feet, as it can get really hot during sunny days in Australia.