At the risk of sounding like a pub quiz: how and when did Pilrig Park Special School do better than the great Pavarotti? Answer: they got a standing ovation after a performance in the Edinburgh Festival Theatre.

The school was back on stage there this month, for the fourth year in a row, but the singing and dancing had an undertone of regret, because Joyce Mudie OBE, the headteacher, was retiring.

It was her “vision” - her depute, Ellen Muir, uses the word of her unaffectedly - that made theatre arts into one of the transforming forces in the school. Curiously, it was never one of Mrs Mudie’s intentions; her preference has always been to make science the framework for learning. But that took second place to encouraging people to develop their strengths and skills, and this includes her staff as much as her pupils. When she came to Pilrig she found her PE teacher “had an absolute gift as a choreographer”.

They started small, with dance groups putting on shows wherever they could. The performances grew. They painted one end of their all-purpose school-hall black, and hired tiered seating.

“I realised that theatre arts was an amazing medium for education,” says Mrs Mudie. “It builds teams. You are creative and at the same time learn to carry out instructions. You work towards an end product. There is an audience, which tells you how successful you have been. Above all, I wanted the children to have ownership of their learning.”

Soon theatre arts were pervading the curriculum, involving almost everybody on the premises. Mrs Mudie’s new timetabling devoted Wednesday afternoons to the preparation, and the audiences were getting bigger. Another venue was needed, and she took the problem “upstairs” to Stevie Manning at Edinburgh’s children and families department and Mary McGookin, head of the council’s arts unit.

“I was expecting a church hall. When Mary McGookin suggested the Festival Theatre, I was blown away,” says Mrs Mudie. “But she could see where we were going. With the bigger stage, we could really expand. We had always had the staff on stage with the children, but now we are able to bring in other adult groups, students from the university, former pupils and colleagues in other schools.”

Ellen Muir, the PE teacher all those years ago, is now the depute, and the “onlie begetter” of these spectaculars. Anyone expecting to find a theatre arts “luvvie” will be sorely disappointed. She is adamant that the learning curriculum is the road she travels, and theatre arts, as far as she is concerned, just happen to be the most useful mode of transport.

“What we do on the stage is not theatre arts,” she says. “It is a celebration of the curriculum. It’s what we do every week of the year. There are no extras.”

She chuckles when I ask about A Curriculum for Excellence. “Creative and innovative learning? We’ve been doing that for 10 years. All I do is turn up in September with an idea: the children take it on from there.”

People ask her if theatre arts are going to be useful. “I tell them, I see children in the maths class struggling to count plastic money. When they are challenged to buy material for the costumes, it means something, it makes sense to them. They will take the measurements and cost the fabric. Children with real reading difficulties are visual learners; in September, they are story-boarding the scenario.

“What we do in the theatre is work experience. The children who work as ushers have to work the whole evening. The discipline is to stay there, after 10 pm if necessary, until the job is finished. And we don’t push the children on stage. If they can’t cue themselves, what have we taught them? Children who can’t sequence to read can sequence 12 or 14 pieces of stage work. Maybe it’s the repetition; maybe the music helps. But it is contextualised in their lives, it is what they do, and for once they are able to compete with the world.”

At their latest performance, the depute had a special tribute to her departing boss. It was a well-kept secret but it involved a newly-written song, the 60 voices of the Edinburgh Schools Gospel Choir and 90 dancers on stage. And another standing ovation.