Directed by Michael Lehmann
Written by Daniel Waters
IMDB

A group of girls named Heather run Westerberg High. They've been considering to let Veronica (Winona Ryder) join their clique. Veronica meets a new kid in school (Christian Slater) and they start dating after he gets suspended for pulling a gun out in school.
The lead Heather asks Veronica to go to a frat party with her. She agrees and when Veronica starts feeling sick and wants to leave Heather says no. Veronica gets sick on the floor and Heather says she's going to tell everybody at school. To get back at her Veronica is going to make her a drink that will induce vomiting. Christian Slater instead pours a cup of drain cleaner. Heather dies and Veronica writes a suicide note in her handwriting. As more people cross Veronica, more people die.
As far as high school movies go this is in my top 10 probably. I love a good black comedy, and this one is very black, although at times goofy. The subject matter (teenage suicide) is very morose, but executed very well. This movie is filled with memorable lines. The only problem I have with this film is the ending. It's not a bad ending, it just could be better maybe.

9/10