Secondly and in addition, a major part of this study is about the effects various influences have on an individuals' intelligence theories and motivation -- effects of expectations, stereotypes, and also teacher behavior in class. Plenty of studies have shown how various external influences have a massive effect on a students' achievement due to the theory on intelligence they form from these influences.
So I agree giving good teachers to everybody is the solution, however there are definitely other environmental factors involved that complicate the issue. For one, breaking up students into gifted/non-gifted categories adds yet another stereotype that could potentially be harmful to both the non-gifted and gifted students.
I believe the solution would encompass having teachers that understand how these influences affect students, which will give them the capability to structure their classes and their instruction in such a way to dissipate any damage these influences can make, and instead turn them into catalysts for growth.
Back then, there was one gifted classroom per grade for the entire school district, and the kids in it were just plain smart. Little 9 year old me, fresh off being hands down the smartest second grader at Audubon Elementary School, was now just about the dumbest kid in class. I could hang with Math, but the reading and writing they were doing in that 3rd grade classroom put me squarely in the remedial group.
Having regular kids in that classroom would have been pure torture for them, and a drain on the rest of the class. Hell, I was a drain on the class at times, and I'd just scored in the 99th percentile on my entrance exams.
I think it's still probably a good idea to split off kids based on ability. This article seems to be more about giving good teachers to everybody, which is certainly a good idea. It just doesn't have any relevance in a discussion about gifted education.