Earlier quoted context omitted.
Equity really isn't the ideology doing this, except in a few cases, it's something else. I'd speculate the dominant effect is that people tend to dislike and resist what they have a hard time imagining: there's a strong bias towards easily-administrated uniformity, and ppl tend to enforce what they know and what they were brought up in themselves
Agreed, and that strong bias is likely driven by cost, not the equity boogeyman that causes many a jerked knee.
When a classmate at the same age is covering material that someone else did three years ago, you will get the tension from both sides, in the same way that it's not all that great socially to be on a traditional school and take classes 3 years ahead.
This issue disappears with all adult students, but around puberty, we are short tools whenever we don't have large enough cadres that we can just put all the kids fast at a given class all together.