John Rosemond:

Over the past 40 years or so, child advocates have given a good amount of lip service to the view that adults, especially educators, should respect children’s “individual differences.”
In theory, this recognizes the fact that every trait is distributed in the general population in a manner represented by the bell-shaped curve. Whether the issue is general intelligence, sociability, optimism, musical aptitude, artistic ability, or mechanical skill (to mention but a few), relatively few people are “gifted” and relatively few people are disadvantaged.
Whatever the characteristic, most folks are statistically “normal.” That is, they possess an adequate amount, enough to get by.
People gifted in more than a couple of areas are rare, and people gifted in one area but lacking in another are not unusual. A person with outstanding musical aptitude, for example, may be noticeably lacking in social skills, and a person with outstanding verbal skills may be mechanically inept.