When they started at the school a year and a half ago, the boys in the special needs science group at Aberdare Boys' Comprehensive were bouncing off the walls: poking each other with pencils, shouting across the room, dropping things they tried to hold and exploding with anger and frustration.
Now in Year 8, the lads I observed one sunny morning in the Welsh valleys were quietly getting on with measuring how much energy it takes to burn a crisp. No talking, no dropping, just getting on with it.
Same boys, same special needs, same teacher. The only difference between a year ago and now is that today the strains of Eine Kleine Nachtmusik waft through the classroom.
It's not an overstatement to say that Mozart has allowed these boys to learn for the first time in their lives.
It all came about by chance when, during October half-term 1994, exhausted science teacher Anne Savan happened to turn on the television one evening. Her exhaustion was the result of an unruly group of Year 7 boys, previously statemented, many of them with emotional and behavioural difficulties, whom she was finding it impossible to teach.
Anne had never taught special needs children and found that ordinary teaching approaches simply didn't work. "For the first half term I couldn't teach them at all. They couldn't even sit on chairs." Along with their behavioural difficulties, she found that they lacked co-ordination, making the simplest science experiments impossible.
Call it fate or just luck, but when Anne flicked on the telly, she found herself watching a film about a French doctor who was working with athetoid spastic children. He had been experimenting with music and found that it had a beneficial effect on their co-ordination.
"He talked about their lack of co-ordination leading to aggression and as I sat there, I thought 'this is like my special needs class.' " Although their physical problems were very different to athetoid spasticity, she saw that her pupils' co-ordination problems were frustrating them and contributing to their bad behaviour. So the first day back after half term, she tried an experiment of her own. She stopped at a petrol station on her way to school and snapped up the only classical cassette on the shelf: The Best of Mozart. She describes what transpired on that first day.
"I came into the classroom and put the tape on before the pupils came in. As usual, I heard them roaring down the corridor. But instead of charging in, they stopped at the door and walked in. Everything was set up for the experiment and I told them quietly what they needed to do. They were silent and went and did it. No one said a word or referred to the music. For the entire duration of the lesson, the boys stayed on task and, for the first time since they had started at the school, didn't quarrel or ask to go to the loo or distract each other in any way. When the headteacher popped in to see how things were going, he was amazed."
Anne decided to trial the background music for five months and found that the pattern set on the first day did not alter. But when she experimented with different pieces of music and different composers, she found big variations. Mozart's contemporaries and more modern composers did not have the same effect on the boys, and neither did piano or choral pieces by Mozart.
She read that researchers suggest that if the limbic system of the brain, associated with co-ordination, is not fully developed in the first two years of life, it can lead to poor co-ordination. But Anne and the researchers believe this could be reversed at any age if the brain is stimulated with high frequency sounds.
She had the boys test each other's physiological responses - blood pressure, pulse rate and temperature - before the lesson without any music, during the lesson with the background music, and afterwards without the music. They found that all the physiological measurements were significantly reduced when the background music was used. With a control group of children who had normal co-ordination, however, there were no physiological changes brought about by background music.
So intrigued and excited is Anne Savan by the findings, which complement those of Dr Sue Hallam and John Price at London University's Institute of Education who have been conducting research using music with a range of children, that she is embarking on a PhD at Reading University to investigate the phenomenon further.
She is putting together a pack, including a tape of specially commissioned music, for use in classrooms and institutions.
As for the boys, they think it's okay, too. Says 13-year-old Nathan Cressey: "The music helps me work a lot better. It makes my work neater and calms down my nerves. But the calmness disappears when we leave the class."
his sidekick, John Michael Jones, says: "We come in here and we're like angels. Some of us were devils before."
Anne Savan can be contacted at Aberdare Boys Comprehensive, Cwmdare Road, Trecynon, Aberdare CF44 8SS. Tel: 01685 872 642