After dark, the 45-year-old teacher often comes to life as a singer, pianist, composer, lyricist, media luvvie and show girl.

But Mrs Perrett’s main mission in life is not to tread the boards of fame, but to revolutionise music lessons. She explains: “As a schoolgirl I hated my A-level music lessons. Now I have a chance to turn it round.”

But not all talented musicians with a postgraduate certificate in education feel the same way, as their quest for stardom takes centre stage. Many drop out of the profession, and others do not even make it.

As Mrs Perrett puts it, “Why be a teacher when you can be pop star or a world-famous harpist?”

Assembly government statistics show Welsh-medium secondaries found music vacancies among the hardest posts to fill last year.

Potentially great music teachers are lost to the profession as they play the fame game, but Mrs Perrett is also convinced a shortage has been created because of “old-hat” teaching methods. Pupils are turned off music at GCSE, very few take it at A-level and even fewer go on to teach it, she believes.

She is hoping to break that pattern with the introduction this year of a Btec in music at Ysgol Bro Morgannwg, Barry, where she is head of department.

More vocational in content than traditional exams, it is all about creating the next Simon Cowell or Cool Cymru band. And whether it is jazz, heavy metal, classical, Salsa or blues, there is music to suit every pupil’s taste.

In a state-of-the-art dedicated music centre with its own instruments and recording studio, it is more like EMI studios than a classroom.

Mrs Perrett hopes it will make music accessible to all and convince more young people to become teachers.

Such is the demand for the new syllabus, she has taken on another member of staff. Bethan Jones did a PGCE at the University of Wales Institute of Cardiff, and did her training placement at the school.

Mrs Perrett said: “I think we would have had real problems recruiting if Bethan hadn’t done her training here.”

As for the lack of Welsh-speaking music teachers, Mrs Perrett sees it simply as a supply-and-demand thing. She said: “Welsh-medium schools are growing, but the number of music teachers are going down - it’s simple.”