DS8 was reading DoWK @ 6 but he also was reading Tom Sawyer, Robinson Crusoe, The Seven Voyages of Sinbad the Sailor, Pinocchio, and Dr. Doolittle.

When he was being tested @ 6.5, the psychologist said Chapter books were a maturity boundary as opposed to a intellectual boundary even among gifted children


DS9 - Starting 9th grade
DS7 - Starting 5th grade