I'm aware of the studies and also of the garbage science like the "Mozart Effect." While they don't support the correlation, they are also not definitive. This appears to be a valid study and it is working. Whether the reasons are because they learn practice and persistence or something else is irrelevant, a correlation still exists. Maybe it's just that music is fun and the way we learn music--practice, reflect, refine, repeat--is a good model for learning in general. It's certainly better than standardized tests. Personally, I don't feel a need to justify music's existence by its value to other subjects. It represents some of humanity's greatest achievements. That should be enough.