Most students will work toward Algebra I in 8th grade
I am still chargrined (bitter?) that 25 years ago my suburban school ended the middle school accelerated English track halfway through my time, but kept the accelerated math “because we can’t make students repeat math classes.” I went from interesting, challenging books to listening to classmates struggle to read books at a reading level I had passed years earlier. And saw a preference for math over reading that I thought was unfair. But your point about discussing the topics, regardless of reading ability, rings true and makes me think there was insufficient support and preparation for what would happen when they made their choice (it was part of a switch from Jr High to Middle School and one of several things to make things more warm and fuzzy, which was not welcomed by those of us caught up in the transition, though I have no idea if it was actually better in the long run for those who came after). If DCPS could do the heterogenous classes well, that probably would help fix the mess I found myself in when the tracking ended.
To be honest, the takeaway I'm getting here is that we need to move to a suburb. The idea that the teacher will be able to teach at different levels in the same classroom is... not at all convincing. And I say this as a teacher myself lol.
I think this is a fair overview of the issues. I can almost assure you that teachers do not have enough training or classroom support to successfully pull off the needed levels of differentiation. DCPS typically likes to do things that look good on paper but don't necessarily have enough classroom voices in central to connect policy decisions with on-the-ground realities.
I would also add, however, that if the most books read was the goal, then we might as all well move out to wealthy suburbs. But we've chosen to live in the city, in part due to convenience, and in part because there is something compelling about living in diverse communities with people of all different walks of life. And it would be silly, in my humble opinion, to live in a diverse city and send kids to a segregated school such that they wouldn't have real exposure to diversity, including socioeconomic diversity. So books read is a good thing, but it also must be balanced with other goals.
Finally, to the extent that poverty exists, there will always be achievement gaps. That is not to say that schools shouldn't try to narrow the gap - they should - but they should also plan for additional supports and differentiation.