Well, to be 12 in 8th grade you'd have to be in KG at the age of 6. All the kids I know hit KG when they're 5 or going on 5.
I'm off a bit, but not entirely.
My oldest daughter and all her classmates in the 5th grade have just turned eleven or are turning eleven. My youngest daughter and all her classmates in the 1st grade have just turned seven or are turning seven over the course of the school year. You do the math.