Why not?
I'm a Welsh speaker who learned English at school, All the Welsh speakers I know are fluent in both Welsh and English from a very early age (5 or 6 years old) something which helped me learn German, Albanian, Russian and Currently I'm learning Spanish
I can get a council form in Urdu, Hindi, Polish but can't get one in Welsh outside of Wales.
May as well make all of these official languages, they're half way there already!
By the way, I agree with Kernow being separated from England
Nome de Guerre, My first language is Welsh, it's what we spoke at home before I went to school. The area I'm from, Anglesey, is over 75% welsh speakers. If they didn't speak Welsh in schools then they wouldn't be able to communicate with the majority of the school.