Gabriella Herrick, a sixth form student at the Greenhill School, Tenby, has achieved Grade 8 Distinction on three different instruments.
Richard Morris, chief executive of the Associated Board of the Royal Schools of Music, said: "This is a very rare achievement and I would like to offer my warmest congratulations to Gaby and the Pembrokeshire Music Service for supporting her studies through to this very high level."
The peripatetic teachers of the Pembrokeshire Schools' Music Service have taught Gaby from an early age. Ken Hewlings and Nicky Thomas taught her the cello and Richard Tiller taught her both the violin and viola.
Head of the Music Service, Chris Llewelyn, said that he had never known such an outstanding achievement. Commenting further, he added: "Gaby's tremendous successes are due to the practice and commitment that she has given to her music. She has been fantastic to teach and we hope that she will be an inspiration to the many young players enjoying their musicmaking with the County Music Service. We would like to thank the accompanists, especially John Thirkettle and Paul Rapi, and also Dr. Stuart Evans, who helped with aural.
Gaby leaves Greenhill this year to follow an art foundation course, before taking up studies at university to become an architect.