Rent Tormented (2009)

Justine, geeky head girl of plush grammar school Fairview High, finds herself hanging out with the in-crowd after school heart-throb Alexis asks her out. All seems perfect...until she discovers the gang hides a dark secret. Darren Mullet already knows what they did last summer: they bullied him until he committed suicide. But death does not stop him taking revenge and one by one, his former classmate get picked off in increasingly brutal and bloody ways.