When signing up for SCAT, do you sign up by what grade they should be in based on age, or the grade of classes they are in?

DS6 is nominally in K, but has reading/la with 3-4 grade, Math with 4th grade. So what test would he take?

Shari
Mom to DS 10, DS 11, DS 13
Ability doesn't make us, Choices do!