A large comprehensive on an estate riddled with social problems, it hit rock bottom six years ago. Only 16 per cent of pupils got five A*-C grades at GCSE and just over half got five grades at any level. Parents were voting with their feet, leaving 800 pupils in a school meant for more than 1,200.
However, since then results have been climbing. Last year, the school came top of the improvement index used by the Welsh qualifications and curriculum authority. This year it has raised the proportion of pupils getting five A*-C grades to 29 per cent, with just over three-quarters getting five A*-Gs.
How has this been done? By entering more pupils for GCSE, for a start. "In the past 10 or 20 years, up to a fifth of pupils at the bottom were entered for other exams," says David Snashall, the new head. "We're moving towards 100 per cent entry for GCSE; the figure's now 97 per cent."
Pupils are also taking more exams; nearly all now take seven to nine subjects. The school monitors the progress of each one. Jill Reynolds, head of history, acts as academic mentor, tracking pupils and persuading colleagues to take the appropriate action.
This term, Mr Snashall has started using information provided by the improvement index to monitor departments and trying to spread best practice. He has also introduced family interviews to get parents involved in raising their children's achievement.
The head pays tribute to his predecessor, Alun Williams, for laying the groundwork for a new start, as well as to a supportive local education authority. Numbers at the school are now up to 1,184.
However, problems remain, notably an 84 per cent attendance rate. Duffryn is working with the education authority to cut truancy by closer monitoring, inter-form competitions and liaison with parents.
So what is Duffryn aiming at now? "I'd like to get to 40 per cent getting five A-Cs, if possible by next summer," says Mr Snashall. "And I think we can go higher."