Overall, I HIGHLY recommend this film.
I do have some constructive criticism however.
Zoey and Lewis don't feel like real characters from the rural, small town US; they seem more like California transplants. Their early morning, large and expensive coffee shop coffee, just isn't a characteristic of high-schoolers outside of California. This along with their style choices just doesn't jive with the setting. These aspects made the characters seem less relatable to me after growing up in a small town.
The blood wasn't extremely realistic either. It wasn't so bad, but was close to looking like an over the top horror film.
Now onto what I liked.
Other than that, Tristan's green jacket was surely symbolic of The Dark Night's Jocker as well as his motives. This also (perhaps unintentionally) bridges Tristan's actions to the "Batman Movie Shooter" in Colorado. Some of his dialog was certainly inspired by the dual boat scene at the end of The Dark Night.
I also admired the the self sacrificing nature of the faculty. It does truly outline what they may be faced with in these sire scenarios.
In closing and summary, I'd say this is a very great Independent film. With perhaps better special effects, and tweaks to the characters, it'd certainly go beyond an independent rating.