I'm with HK on this one. The study doesn't show that early school entry and reading are bad for gifted kids so much as it shows that school is bad for gifted kids.
Also, the Terman study is known to have enough issues due to selection criteria. Then Kern/Friedman made the problem worse by applying this:
2.2.1. Age of learning to read
In 1922, parents specified the age their child began to read (“Did your child learn to read before starting school? At what age?”). As the average student was almost twelve years old when first studied by Terman, the average time lag from age of reading to parental report was 5.94 years (SD = 2.91 years); this time lag introduces some unreliability and so any associations that emerge may underestimate the size of the true effect.
2.2.2. Age at school entry
In 1922, parents also noted the age and grade their child began attending school (“Age of entering school above kindergarten”) and whether or not the child attended kindergarten. School entry age indicates the participants’ age upon starting first grade. The average time lag between starting school and parental report was 5.97 years (SD = 2.79 years), which again introduces some unreliability that may underestimate true effect sizes.
If the data upon which they're going to base any conclusions is unreliable, so then are the conclusions.
Plus, when you ask a parent, "When did your child first begin to read?," this begs the question, "What do you mean by 'read'?" We've seen in our discussions here how we sometimes have different meanings of the term.
