These days no one is ready to talk about cultural and behavioral differences that lead to different outcomes, but it is the most obvious cause of disparities in education and career success between ethnicities. The reason policies like affirmative action or gutting gifted education are discrimination to me, is that students from certain backgrounds are being punished for their cultural and behavioral differences. For example, most Asian cultures emphasize a focus on hard work, academic success, respect for your elders, etc. Anyone who has spent any time in the American schooling system knows that Asian students have remarkably different behavioral patterns from white or black American students. They make choices that lead to their success, and now they’re being discriminated against by those claiming there are “too many” successful Asians. A similar argument can be constructed for other groups.
The 30% of black and Hispanic students who were already in Boston's gifted program by virtue of their intelligence are now also going to be discriminated against in order to pack the advanced classes with their less intelligent peers. This will push the black and Hispanic students already qualified for the program out.
Heather Mac Donald wrote about behavioral contributors to disparities and other issues stemming from a societal overfocus on diversity in The Diversity Delusion (https://us.macmillan.com/thediversitydelusion/heathermacdona...). You can read a brief contribution from her regarding behavioral drivers of socioeconomic disparities (like crime rates) at https://www.newsweek.com/if-systemic-racism-real-why-does-bi....