I don't get how "siphoning off" the percentage of the student population that scores in both the 98th percentile on the cogat and the 95th percentile in achievement can in any noticeable way affect the rest of the student population, or how distributing them across the district could in any way make a noticeable difference in classroom diversity.
Agreed. Until recently, even distribution of students in public school classrooms was said to be fair to the public school teachers who were rated/evaluated in part on a comparison with other teachers, of overall classroom achievement test scores.
Therefore to be "fair to teachers", if 20 students were to be distributed among 4 teachers, one might anticipate the pupils to be distributed this way (by inbound ranking of the pupils' achievement test scores):
Teacher W is assigned pupils 1 & 20, 5 & 16, 9
Teacher X is assigned pupils 2 & 19, 6 & 15, 10
Teacher Y is assigned pupils 3 & 18, 7 & 14, 11
Teacher Z is assigned pupils 4 & 17, 8 & 13, 12
working through the highest and lowest student rankings toward the middle.
More recently, public school teachers are not only rated/ranked/evaluated on overall classroom scores, but by scores by demographic... specifically by closing the achievement gap and/or excellence gap. This entails stagnating the top students so that the lower students are making comparatively greater gains.
I find this practice to be unconscionable. Again, I'll contrast the current "equal outcomes" educational goals of American public schools with the acknowledgement of exceptional athletic talent... and the need to nurture it... which we see at the Olympics.