I think 2 x 30 minutes a week is more valuable than 1 x 45 lesson, FWIW. Also joining a choir and learning recorder as well at that age would be a good idea for a very talented child.
(I was one, btw, and am now a qualified music teacher, voice and piano. I also sang professionally for a bit).
At primary school I did a bit of recorder, about 15 minutes a week, plus a very good RSCM choir.
By upper secondary school I was doing 60 minutes voice, 30 minutes piano and 30 minutes violin a week, plus 3 choirs (including another RSCM one and a semi-professional choir), orchestra and so on.
At music college we had 60 mins a week first study, 30 mins a week second study, plus for first study we also had repertoire, recital, music theatre and opera classes (60 minutes a week each) and for second study we had 60 mins a week keyboard harmony. (We also did things like choral conducting, orchestration, harmony and counterpoint, and so on).