Which Grade is Supriya in?

As we were driving back from Harmony Hill, Supriya asked me, "Am I in the second grade?" I said, "No, you are in the first grade. You will be in the second grade in September." Then I expanded, "But I don't believe in grades. You are singing at about 4th grade level, and you are reading at first grade level. Grades don't mean much." I don't know if she understood what I was talking about.

That conversation led me to this interesting thought. Grades are often used as proxies for age, but they can also be indicators for proficiency or level of accomplishment. And then for each of the thousands (millions?) of human activities, one could earn a grade. For example, Supriya's would be: Singing - 4, Reading - 1, Math - 1, Gymnastics - 3, Swimming - 1, Roller-skating - 3, Drumming - 3, People Management skills - 4, Clowning - 3, Music History - 4, Acrobatics - 4 etc. So which grade is she really in?...