Not the same thing. Showing a correlation between the number of years of schooling a person had and their IQ is not the same as a decrease in IQ before and after schooling.
"In one 1932 study of children living in Virginia's Blue Ridge Mountains, the I.Q.s of 6-year-olds were "not much below the national average, but, by age 14, the children's I.Q.s had plummeted into the "mentally retarded range," with the degree of falloff directly related to the years of school the child had missed. Likewise, a study done in the 1980s shows that I.Q. scores for kids on summer vacation drop by a statistically significant amount, as compared to their I.Q. scores before vacation. Swedish psychologists found that finishing high school bumps up I.Q. by about 8 points over what it would be if the same child had dropped out after junior high. Likewise, an American research team found that every year of schooling increases I.Q. by about 3.5 points."
Believe me, this subject has been studied quite a bit.
(however "gifted learners" are defined). Another concern about United States schools is that they appear to badly underperform compared to schools in many other places, for learners of all ability levels.
Concerns of these kinds have motivated hundreds of college-educated parents I know to choose to homeschool their children, to make sure the children aren't slowed down academically. Some seventeen-year-olds find it fun to study abstract algebra with the Artin textbook (through dual enrollment at the local university as a "twelfth grade" homeschooler) or algorithms with the Cormen textbook. The standard K-12 school curriculum doesn't fit all learners, and especially not the most able learners.
http://books.google.com/books?id=hbJB6z5dZswC&pg=PA70...