Their kids will then mop the floor against all other kids, including engaged kids without engaged parents, that would have benefited from more advanced classes. Is that equality?
Without this measure, the kids that are not able to follow classes that needs things they cannot afford will just fail the lecture and drop from school, from THE WHOLE SCHOOL.
Without the measure, you have people who drop out of school and get a mathematical education close to 0 and will compete with people of mathematical education of 10. With this measure, the same people will get a mathematical education closer to 5, and will compete with people of mathematical education of 10.
But as the parent post points out, 10s either dominate the class, leave the class, or ignore the class and take math outside school. None of that help's the 5s, and all of it hurts, or is wasteful for the 10s.
So, I'm now not even sure where this "dumbing down" the students comes from. Maybe it's yet another moral panic.
You have to look further back. They are blocking middle schoolers from taking Algebra. That means they won't haven't progressed enough to get to Calculus unless they skip ahead a grade level of math, either via summer school, or other outside study.
By replacing it by another challenging mathematical content. How is that "dumbing down".
It's like saying "they are making students less musical because they are replacing piano lectures with guitar lectures".
And, yes, I get that Algebra is not the same as Data Science, and that Algebra may cover some foundation needed for a math specialization. But a lot of students don't end up doing a specialization in math: for them, Data Science may make them SMARTER than Algebra which give tools rather than train the brain to think differently.
I had a strong math cursus at uni, and I've observed that it takes a while for the "math point of view" to "click" and suddenly make sense. It is also the case in some comments here. I have never seen someone saying they have "clicked" before uni (I'm sure there is some, the point is that they are too rare to be the reason we waste all the other students' time). The reality is that teaching 1 year of something that you need 2-3 years before "clicking" means that it is just wasted on people who just do one year.
And, of course, Algebra is not limited to that. But it is also just true that a lot of it is learning formula by heart, which makes it difficult to pretend teaching a more challenging, engaging and practical math domain will make people somehow less smart.