Solution: Bring back tracking. Top to bottom, with 10, or at most 15 IQ points range (or whatever measure of ability is relevant to the class topic).

90th percentile students (IQ 120) should not have to share a classroom with 50th percentile students (IQ 100). They are just too different.

It is indefensible to believe that gifted students have a right to a separate class from the rest, without also believing that 90th percentile students (IQ 120) students have a right to a separate class from 50th percentile students (IQ 100).

There. I've said it.