The seven-year-old has just earned a London College of Music Grade 8 Distinction in electric guitar, a qualification usually gained by students seeking to study degree level music.
Alexander, of Pudsey, is now studying an Open University London College of Music course.
He practices for around three hours-a-day after school and for anything up to six-hours-a-day at weekends.
Pudsey Southroyd Primary School pupil Alexander draws big crowds when he busks in Leeds city centre with his guitar tutor Jamie Holroyd, of Beeston.
Mr Holroyd, 26, said: “He is exceptional. He has got the potential to do anything he wants in music. He is already professional musician standard now. I think he will become a worldwide name as a performer eventually.”
Alexander’s mother Annie, 32, said he started playing guitar aged three and soon mastered Deep Purple’s Smoke on Water.
Mrs Santarpia said Alexander can now play complicated technical songs by respected guitarists including Joe Satriani and Steve Vai.
She said: “He just enjoys playing. He has always said he wants to be a rock star from when he was very little.”
Heavy metal fan Alexander’s favourite bands include Metallica, Slipknot and Black Sabbath. His favourite guitarist is the late Randy Rhoads, who played with Ozzy Osbourne.
Alexander said: “I want to be a rock star – I love music. I need to practice a lot to get it right.”