It may seem a big jump from depression and self-harming to romantic fiction, but children’s writer Jo Cotterill has made the transition. Her first full-length novel – written under her maiden name of Joanna Kenrick — was Red Tears, the story of 15-year-old Emily, who starts self-harming in the run-up to her GCSE exams.

Her second book, Screwed, dealt with under-age sex. She wrote the books while teaching English at Wychwood School in Oxford, and they were acclaimed for tackling difficult issues in a page-turning style.

But then she had a bright idea — for a series called Sweethearts, a “feel-good new series of first-kiss fiction” which took her into a more commercial market and won her a six-book contract from Random House.

She said: “When I told my agent about the idea, she saw it would fill a gap in the market. Publishers have been concentrating on boys for the last few years, and now they are looking for stories for girls.

“It is a completely different type of book — very happy and light-hearted, but still concerned with girls' friendships as well as relationships with boys.”

The deal with publisher Random House allowed her to give up teaching and write full-time. She uses her married name for the ‘first kiss’ series, having written her young adult books as Joanna Kenrick.

She doesn’t believe she is unusual in having vivid memories of her own childhood, which she draws on in her books.

“I had a very happy childhood. I know a lot of writers draw on bad memories, but I was very happy. What sticks out, though, are those very intense moments when everything seems so important — what you wear, who your friends are. Things like having the wrong pair of shoes seemed to matter so much, and I do remember feeling that that was the end of the world.”

Her background in theatre — she has a degree in performing arts and worked as an actor for five years before taking up teaching — means that her books are full of action, keeping her readers turning the pages.

Many of her Sweethearts characters are also in love with the stage, and the first book in the series, Star Crossed, tells the story of a school production of Shakespeare’s Romeo and Juliet. At the auditions, Fliss lands the part of Juliet, against stiff competition from the class bully, Samantha.

Fliss is too shy to tell her Romeo how she feels about him. So he starts going out with the evil Samantha, Fliss’s rival in love and on the stage.

How does Jo manage to capture the inner world of teenage girls — and their language — so accurately?

She says most of her material comes from her own imagination, but she does draw on her contact with present-day teenagers to keep her slang up to date. “People say to me ‘Do you get ideas from your pupils?’ and I don’t really, except for the way they talk to each other. They use different language now, and it keeps me in touch.”

Having grown up in Appleton, she now lives with her husband and young daughter in Long Hanborough, where she writes in a shed in the garden.

She said: “The back garden has the most wonderful view and we actually only bought the house because of it. In October 2007 I had a writing shed installed, which looks out over the view, and which I use year-round depending on weather.”

The Sweethearts launch party was at Matthew Arnold School, Cumnor Hill, where the head of English, Natalie Kemmitt, found her students responded enthusiastically when they were invited to get involved.

Jo said: “I asked if the students would be interested in making a video to launch the book. A lot of books have a trailer on YouTube, because kids spend a lot of time there.”

Just like the girls in Jo’s fictional town of Parchester, the Matthew Arnold students proved themselves full of imaginative ideas, producing a roomful of romantic activities and a real-life gold-sprayed cupid for the launch evening.