For 12 years, Vivienne Franzmann worked as a drama teacher in several North London comprehensive schools.

In 2008 she wrote a play — based on a true story — that premiered in Manchester last year and then transferred to the Lyric, Hammersmith; she won awards and a review in a leading national newspaper saying that it was “quite possibly… the play of the year”.

Franzmann has given up teaching now in favour of full-time writing, but it is her debut drama Mogadishu that comes to the Playhouse next week for Oxford to pass judgment on all these accolades. The plot is very modern, very edgy and tough.

“It came from a friend of mine,” she told me, “who had been accused of something in a school. It was about . . . well, I don’t want to say in detail because she was caught up in a false allegation; but what was interesting in her story was that students colluded in the accusation knowing it wasn’t true. And that’s something that doesn’t often happen in schools because children do usually tell the truth. So, in my play, I explore what the factors might have been that drove the students to collude”.

Because of her reticence, I assume that the plotline of Mogadishu does not follow exactly the experience of her friend. It entails a teacher, Amanda, being pushed to the ground by Jason, a black student, when she tries to stop him fighting with another pupil. She doesn’t report the incident for all the right reasons, but Jason does — backed up by some of his mates in claiming that it was Amanda who pushed first and racially abused him. The head teacher believes them and the whole situation spirals horribly out of control.

I ask Franzmann why she chose title — Mogadishu, of course, being the ravaged city in Somalia where, in 1993, US forces were caught up in the incident translated into the action film Black Hawk Down. “There’s the concept of conflict, of course, but I always think Mogadishu is one of those places people kind of think they know what went on there, but don’t really; so, everybody’s been to school and think they know about schools — and if you went to a good school, you do know, but you really don’t if we’re talking about a difficult or challenging school”.

SHE always wanted to write a play, but without a deadline of some sort, and not knowing what to do with the finished object afterwards, she felt the exercise would be purposeless. Then her partner spotted the Bruntwood Playwriting Competition and Franzmann found purpose. That was followed by the annual George Devine Award for Most Promising Playwright in 2011.

Vivienne Franzmann rather insouciantly doesn’t take anything for granted, but the writing of Mogadishu has changed everything: for example, she was commissioned by the Royal Court Theatre to write a second play: “Their new literary manager had read Mogadishu and I went in for a meeting and he asked me if I had another idea and I told him and he commissioned me. It was all very straightforward, really!”

The new play is called The Witness and is a smaller affair, with only three characters. “It’s about a retired war photographer who took a famous photograph in Rwanda during the 1994 genocide. It takes place in the present day and there are lots of secrets involved”.

The curtain of reticence comes down again, although she did say that this time the plot isn’t based on a true story. The play will have its first outing in June.

Franzmann is also the writer-in-residence for a theatre company which helps ex-offenders and has discovered she can write plays for radio (her first comes up in April). “If I’d been told about the journey at the start, I wouldn’t have believed it!”

Mogadishu is at the Oxford Playhouse, February 14-18.