When I was 12, I was reading at college level, or so the tests told me. I don't remember much from sixth grade, but I do recall my class read "The Count of Monte Cristo". That was a challenge.
Back then, in the 60s, California public schools were very good.
Yep, I remember topping out with 16th-grade scores pretty much across the board on achievement tests when I was in 5th and 6th grades. Has ever made me skeptical of education when I read about students reading at grade level or, gulp, below.