Excellence vs Equity in the Classroom. Inflammatory Classroom Techniques?

"Heresy!  I say, "Heresy"!  Focusing on "excellence" rather than "equity" in math education?"

A fellow traveler in education circles sent and remarked (above) on an article from Educational Leadership praising the long discarded teaching technique of ability grouping in the classroom:

 

A school in Arizona was able to curb the exodus of its top students to nearby charter schools by clustering students in the classroom. In cluster grouping models, all students in a grade level are grouped according to their ability and achievement levels. A cluster of either gifted or high-achieving students -- one or the other -- is in every classroom, along with only two or three other clusters. The method allows teachers to spend more time with individual students and gives gifted students a better chance to excel, according to Dina Brulles, director of gifted education services at Paradise Valley Unified School District in Phoenix, and Susan Winebrenner, founder and president of Education Consulting Service.