As mentioned in other comments, there are a lot of confounding factors. One of the big one is the selection bias by parents. I would guess that most musical t

As mentioned in other comments, there are a lot of confounding factors. One of the big one is the selection bias by parents. I would guess that most musical training starts in childhood and is facilitated by parents. Also, most parents who are this involved would place schoolwork above musical training. Thus, the kids enrolled in musical training are ones that are doing well in their classwork.