I think he was 12 when this was recorded so he would not have been in any high school at the time. Considering he is a native Welsh speaker who learned English just before stating school and then Latin when he became a chorister at 8, don't you think it a bit much for him to master Italian pronunciation and diction by age 12? Check out "Aled Jones Boy Soprano in 'The Treble'" for his story.
The first time Ombra Mai Fu appears on an album by Aled, he was 14 years old, therefore he would most definitely have been in high school. If you read Aled's autobiography, he reveals that in the lead up to recording his first album, he learnt all the songs in English, Welsh, Italian, Latin and German (just for good measure) thus proving that nothing was beyond him, despite his young age :)