The title, Schools Don't Kill People, is a play on the slogan, "Guns Don't Kill People...". The full slogan as I have paraphrased it is, "Schools Don't Kill People, Teachers Kill People."

Four rookie teachers start at a high school. Two find their twin destinies in life; to become serial killers and to fall in love with each other. The other two, Lance and Pat, want to break up their love.

Act I is the journeys from twisted childhoods to first kills of the protagonist Bob and the antagonist and love interest Ellen and their meeting, instant attraction, and rivals.

In Act II, Bob and Ellen kill again and again as their relationship grows. Pat and Lance each pursue Bob and kill. Bob and Ellen each find out the other is a serial killer and join forces, leading to their engagement. Pat and Lance, and seniors Kellee and Kortnee, who have a crush on Bob, all try to break Bob and Ellen up, seeming to have succeeded.

Act III starts with Kortnee making her play for Bob and all the characters making their big moves in a running epic battle between Bob and Ellen that leaves leaves everyone else dead on their path to a final showdown and moment of fate.

The denouement shows their fate and if they have a future.

Schools Don't Kill People is a dark action/thriller/romance/comedy (a rom-com). So, really, it's not a story about serial killers at all, but a boy-meets-girl story. The true heart of the story is Bob and Ellen's romance.

P.S. Don't bother looking for positive character arcs.