The answer to the OP's question will depend on the relative importance one ascribes to academics and sports, and a forum for academically gifted children may tend to attract parents whose especially value academics. Most people here do not favor foregoing an academically justified grade skip for athletic reasons, but if the same question were asked in a forum for parents of gifted athletes, the majority opinion could be different.
A book I really liked
Developing Talent in Young People (1985)
by Dr. Benjamin Bloom
has chapters on various types of talent, including swimming. The chapters are as follows:
The Nature of the Study and Why It Was Done
Learning to Be a Concert Pianist
One Concert Pianist
The Development of Accomplished Sculptors
The Development of Olympic Swimmers
One Olympic Swimmer
Learning to Be a World-Class Tennis Player
The Development of Exceptional Research Mathematicians
One Mathematician: Hal Foster
Becoming an Outstanding Research Neurologist
Phases of Learning
Home Influences on Talent Development
A Long-Term Commitment to Learning
Generalizations About Talent Development
