Bitter experience has taught me to not have high hopes of teachers who turn their marking hands to writing. For every Philip Pullman, there are 100 teacher-writers who would be best advised not to rip up the lesson plans just yet.

But Annabel Pitcher is not one of them. The former English teacher’s second novel for teenagers, Ketchup Clouds, tells the story of 15-year-old Zoe who, in a succession of letters to a murderer on death row, gradually confesses a dark secret.

From the start, Zoe (this is a pseudonym: she is worried the murderer might escape and hunt her down) is eminently likeable. She says things such as: “Everyone’s got good and bad inside them. Everyone. Even people you don’t expect to have a dark side, eg, Barack Obama and Blue Peter presenters.”

And, poignantly, her one-way relationship with the convict progresses from “Dear Mr Harris” to “Dear Stuart”, through to “My dearest Stu”.

The plot unfolds at a delectable pace. Zoe confesses to Mr Harris (as he is at this stage) that she has killed a boy. She then tells him how, at a house party the previous year, she fumbled drunkenly with cool-boy Max, and then bonded more cerebrally with a mysterious boy with brown eyes.

Gradually, her relationships progress with both Max and brown-eyed Aaron. The sexual tension crackles with the turn of the page: we are left in no doubt as to which boy she really likes. But, with masterful control, Pitcher conceals as much as she reveals and we remain no closer to knowing which of the boys has died.

Meanwhile, Zoe’s home life is portrayed in vivid detail. While certain elements are clearly plot drivers - the dying grandfather, the deaf sister, the arguments between her parents - they also create a complex and realistic portrait of family life.

Admittedly, the narrative tone is not always consistent. There are laugh-out-loud moments, such as when Zoe refers to A Christmas Carol and says: “If you’ve never read Dickens or seen The Muppets, then let me explain.” There are moments of lyricism: “Our stories, our secrets - all of it would disappear, hovering in the darkness like smoke, before fading to nothing.”

There is a lot of Dawson’s Creek-style wordy precociousness. There is also unequivocal teenageriness: “No offence or anything, but I can’t imagine you have many friends on death row.”

And, sometimes, there are all four styles, within the space of a few paragraphs.

Still, as quibbles go, this is a minor one. Overall, Ketchup Clouds is smart, funny, moving, suspenseful and psychologically astute. Any would-be teacher-writers could do far worse than use this as their model.

Ketchup Clouds by Annabel Pitcher is published by Orion, #163;9.99.