More able students - time to set them free?

In every public school classroom there are more able, less able and ordinarily able students.

For as long as more able students have been in public school classrooms, they have been held back in their education while less and ordinarily able students were taught and retaught the same material.

For as long as less able students have been in public school classrooms, they have fallen further and further and further behind until they drop out.

There is no reason why students cannot acquire education at their own individual speed.  There is no reason a student cannot be expected to master material, however long that takes, before moving to the next.

Even if you could take 30 kids with nothing in common but their age and then form them into thought choirs who can learn in unison, why would you want to?

What purpose would does serve?

If the goal of public school education is to create independent lifelong learners, why is it not the immediate objective?