This is called an "integrated classroom" which is part of the "differentiated learning" pedagogy [1].
It has been around for a very long time.
Many schools have incorporated it into their curricula.
It is extremely difficult to build a successfully integrated classroom. The kids who need more help will slow down the kids who need less, which can decrease performance in both groups.
Educators with integrated classrooms need to construct several variations of a single lesson plan to mitigate this.
Given that education is amongst the lowest-paying professions in the US (less well-paying than restaurant work, after tips!), and given that many schools have been stripped of funding and other resources that can help alleviate this potential burden, I hope you can see why implementing this suggestion is easier said than done.
[1] https://en.m.wikipedia.org/wiki/Differentiated_instruction
Remote school was a disaster for younger kids. All schools- public or private- are bureaucracies with rigid hierarchies. The pandemic showed the cracks in many social institutions. Schools were no exception. With a more horizontal and open structure, schools could have responded more flexibly.
Also there should have been a massive social safety net similar to the Great Depression supporting families AND businesses during the worst of it so parents could just be with their families.
In a vertical market-based Capitalist social structure, there just is very little wiggle room and the system fights like hell to maintain its own homeostasis.
A pandemic is classic example of a situation that would benefit from Capitalism stepping aside and let Socialism handle the hard stuff during the crisis- until Capitalism can step back in. It doesn't have to be binary. To not embrace this kind of flexibility is like building a structure in an earthquake zone with no provision for movement. It's going to fail during times of stress.