well if we just apply the bell curve here, on average children will be pretty average (shocker) so those should be left on their own and discover their own niche while bad performers should get extra attention so they can keep up with the rest and with the gifted (if they actually want to) given the opportunity to explore higher level subjects.

so in the end we give attention to gifted and the struggling since there's very little you can do to children who are already decent and are capable of keeping up at most they lack discipline or motivation.

Gifted and average students who aren’t given attention become poor performers quickly.

Gifted students especially.

Students who learn ahead don’t want to be told: “ok you have the material, so I’ll ignore you for a bit.” They want more. They want their questions answered, even if the questions aren’t part of the lesson plan.

Nobody wants to be told “we aren’t studying that today.”

You really can’t starve the rest of the class to cater to poor performers.