A lesson runs at the pace of the slowest students, and those slowest students don't want to learn and actively disrupt the class and everyone else. We tolerate this far too much its damaging to the other 20-30 children in the same lessons and moving them to their own classes would have a much bigger average impact than picking the brightest for special lessons. Ideally we would do both so people could go closer to their pace.
This is not a fair assumption and is what leads to kids in remedial classes not getting a decent education.
Kids can be genuinely disruptive or not care, or they can care but struggle with the material, those are orthogonal traits.
I don’t disagree that the lesson goes at the pace of the slowest students, but those slow students deserve a disruption-free classroom too, even if it moves slower than the advanced class.
